Ruby

Last updated: 2026-06-29

The rustpdf gem wraps the rust-pdf C core with idiomatic, chainable classes over Ruby's built-in Fiddle standard library (pure FFI, no native gem to compile). It covers the whole product surface: vector graphics, embedded/subset fonts & Unicode text, paragraphs, images, PDF/A (1b–3a + A-4/4e/4f), tagged/accessible output, attachments, AcroForm fields, manipulation, text extraction, encryption and digital signatures.

Installation

Install from RubyGems. The native library (libpdf_ffi) ships inside platform-specific gems. macOS has arm64-darwin, x86_64-darwin and a fat universal-darwin (x86_64 + arm64); Linux has x86_64-linux and aarch64-linux; Windows has x64-mingw-ucrt. RubyGems downloads only the gem matching your OS and architecture, so there's nothing to compile.

gem install rustpdf
# or in a Gemfile:
#   gem "rustpdf"

Requires Ruby 2.6+ (Fiddle is bundled with the standard library). Verify it loaded:

require "rustpdf"
puts RustPdf.version   # native library version

Quick start

A one-page document with a filled rectangle, saved to disk:

require "rustpdf"

doc = RustPdf::Document.new          # A4 by default
doc.add_page
   .fill_rgb(0.86, 0.20, 0.18)
   .rect(72, 640, 200, 120)          # x, y, width, height (points)
   .fill
doc.save("out.pdf")
doc.close

Most methods return the document, so calls chain:

doc = RustPdf::Document.new
font = doc.add_font_file("Roboto-Regular.ttf")
doc.add_page
   .fill_rgb(0.1, 0.1, 0.12)
   .rect(0, 800, 595, 42).fill
   .show_text(font, 24, 72, 740, "Olá, açúcar — café")
data = doc.to_bytes                  # a String of bytes instead of a file
doc.close

Licensing & activation

Basic generation (everything above) is always free. The corporate features (PDF/A, digital signatures/PAdES, encryption, accessibility) require an active license token. Without one, those calls raise RustPdf::Error and produce no output.

Activation needs no rebuild. Easiest is an environment variable, auto-activated the first time a corporate feature is used:

export RUSTPDF_LICENSE="010f0000…"           # the token we email you
# or point at a file:
export RUSTPDF_LICENSE_FILE=/etc/rustpdf/license.txt

Or activate explicitly in code:

RustPdf.activate_license(token)   # raises RustPdf::Error if forged / expired / malformed

Coordinate system

• Units are points (1 pt = 1/72 inch). A4 is 595 × 842, US Letter 612 × 792.
• The origin (0, 0) is the bottom-left corner; y grows upward.
• For text, (x, y) is the baseline of the first glyph.
• Drawing/text always targets the most recently added page.

Threading & concurrency

Every native call is synchronous and the core is Send but not Sync: a single handle must never be touched by two threads at once.

• Documents are independent. Each Document/EditableDoc shares no state, so they're safe to build across threads or processes, one handle per thread.
• Don't share a live handle between threads; give each its own.
• Errors are per-thread. The native last-error is thread-local, so a failure in one thread never clobbers another's, and RustPdf::Error surfaces on the calling side.
• License is process-global. activate_license (or the env var) applies to every thread; activate once at startup.
• The GVL: a long generation holds Ruby's global VM lock for its duration. For heavy parallel jobs, fan out across processes (e.g. a job queue), one document per worker.

Authoring: create & save

Creates an empty document (A4 default page size). Call close to free the native handle.

Pages & vector graphics

Graphics state and path operators mirror PDF's content-stream model. Colors are RGB in 0.0–1.0.

doc = RustPdf::Document.new
doc.add_page
   .stroke_rgb(0.10, 0.45, 0.90).line_width(3)
   .rect(72, 600, 300, 160).stroke
   .fill_rgb(0.95, 0.77, 0.06)
   .rect(120, 640, 120, 80).fill
doc.save("shapes.pdf")
doc.close

Fonts & text

Fonts are embedded and subsetted, with HarfBuzz-quality shaping, kerning and full Unicode (Type0/CIDFontType2 with ToUnicode, so text extracts and copies correctly, provided the embedded font covers those characters). Register a font once, then reference it by its integer id.

heading_level (1–6) tags the run as H1–H6 in an accessible document (see Accessibility); leave it out (or 0) for ordinary text.

doc = RustPdf::Document.new
regular = doc.add_font_file("Roboto-Regular.ttf")
# …or from bytes you already have in memory:
# regular = doc.add_font(File.binread("Roboto-Regular.ttf"))

doc.add_page
   .show_text(regular, 28, 72, 760, "Invoice #1024")
   .show_text(regular, 12, 72, 720, "日本語 · Ελληνικά · العربية")
doc.save("text.pdf")
doc.close

Paragraphs

The paragraph layer wraps, aligns and justifies text inside a fixed width (greedy line breaking using shaped glyph widths).

intro =
  "A long paragraph that wraps to the given width and is justified " \
  "automatically; extra space is distributed between words."

doc = RustPdf::Document.new
f = doc.add_font_file("Roboto-Regular.ttf")
doc.add_page
   .paragraph(f, 12, 72, 700, 451, intro, align: RustPdf::Align::JUSTIFY)
doc.save("paragraph.pdf")
doc.close

See the Align enum for the alignment options.

Images

JPEGs are embedded verbatim (DCTDecode, no re-encode). PNGs are decoded and re-encoded (FlateDecode); alpha becomes an /SMask, palette becomes an Indexed color space. Register an image once, draw it many times.

doc = RustPdf::Document.new
logo = doc.add_image_file("logo.png")
doc.add_page.draw_image(logo, 72, 680, 160, 90)
doc.save("with_image.pdf")
doc.close

PDF/A licensed

Produce archival-grade output. pdfa defaults to A-2b; pass a Pdfa level for a specific one. An embedded sRGB ICC profile, output intent, XMP metadata and document /ID are added automatically; A-1b also forces PDF 1.4 and emits a /CIDSet, and A-4 (ISO 19005-4) is based on PDF 2.0.

doc = RustPdf::Document.new
doc.pdfa(RustPdf::Pdfa::A2B).info(title: "Q3 Report", author: "Acme Inc.")
f = doc.add_font_file("Roboto-Regular.ttf")
doc.add_page.show_text(f, 20, 72, 760, "Archival report")
doc.save("report_pdfa.pdf")     # raises RustPdf::Error without a license granting PDF/A
doc.close

Accessibility (Tagged PDF / PDF/UA) licensed

tagged builds a logical structure tree (PDF/UA-1). Combine with pdfa(RustPdf::Pdfa::A2A) for archival and accessible output. Use heading_level: on show_text for H1–H6, and figure(..., alt) for described images.

doc = RustPdf::Document.new
doc.pdfa(RustPdf::Pdfa::A2A).tagged.info(title: "Accessible report")
f = doc.add_font_file("Roboto-Regular.ttf")
doc.add_page
   .show_text(f, 26, 72, 760, "Annual report", heading_level: 1)   # H1
   .show_text(f, 14, 72, 720, "Overview", heading_level: 2)         # H2
   .show_text(f, 11, 72, 690, "Body paragraph of the section…")
chart = doc.add_image_file("chart.png")
doc.figure(chart, 72, 520, 300, 150, "Revenue grew 18% year over year")
doc.save("accessible.pdf")
doc.close

Attachments (PDF/A-3) licensed

PDF/A-3 allows embedding arbitrary source files (e.g. the XML behind an e-invoice). Each attachment carries a MIME type and an Relationship.

xml = File.binread("invoice.xml")
doc = RustPdf::Document.new
doc.pdfa(RustPdf::Pdfa::A3B).info(title: "E-invoice 1024")
f = doc.add_font_file("Roboto-Regular.ttf")
doc.add_page.show_text(f, 18, 72, 760, "Invoice 1024")
doc.attach_file("invoice.xml", "text/xml", xml,
                relationship: RustPdf::Relationship::SOURCE,
                description: "Structured invoice data")
doc.save("einvoice.pdf")
doc.close

ZUGFeRD / Factur-X e-invoices licensed

Turn the document into a ZUGFeRD / Factur-X electronic invoice: the embedded XML (the Cross-Industry Invoice) is attached as factur-x.xml, the file is marked PDF/A-3, and the Factur-X identification is written into the XMP metadata. The visible PDF is the human-readable invoice; the embedded XML is its machine-readable twin. Validates as PDF/A-3 + Factur-X under veraPDF.

xml = File.binread("factur-x.xml")         # your Cross-Industry Invoice XML
doc = RustPdf::Document.new
doc.info(title: "Invoice INV-2026-001")
f = doc.add_font_file("Roboto-Regular.ttf")
doc.add_page.show_text(f, 18, 72, 760, "Invoice INV-2026-001")
doc.facturx(xml, profile: RustPdf::FacturxProfile::EN16931)
doc.save("einvoice.pdf")        # PDF/A-3 + Factur-X; needs a PDF/A license
doc.close

See the FacturxProfile enum for the conformance levels (MINIMUM to EXTENDED).

AcroForm fields

Build interactive forms with generated appearance streams (no NeedAppearances). Rectangles are [x0, y0, x1, y1] arrays; page is a 0-based page index. Dotted names ("a.b.c") create hierarchical fields.

doc = RustPdf::Document.new
doc.add_page
   .text_field("applicant.name", 0, [72, 700, 320, 720], value: "")
   .checkbox("agree", 0, [72, 660, 88, 676], false)
   .dropdown("plan", 0, [72, 620, 240, 640],
             ["Starter", "Pro", "Enterprise"], selected: 1)
   .radio_group("billing", 0, [
     [[72, 580, 88, 596], "monthly"],
     [[140, 580, 156, 596], "annual"],
   ], selected: 1)
doc.save("form.pdf")
doc.close

Fill and flatten fields later with EditableDoc.

Hyperlinks free

Add clickable link rectangles to the current page: a web link opens a URL; an internal link jumps to another page (optionally scrolling so a given top y-coordinate sits at the top of the view).

doc = RustPdf::Document.new
f = doc.add_font_file("Roboto-Regular.ttf")
doc.add_page.show_text(f, 14, 72, 760, "Visit rustpdf.dev (see page 2)")
doc.link_uri([72, 756, 320, 776], "https://rustpdf.dev/")   # web link
doc.link_to_page([330, 756, 430, 776], 1, top: 800)         # jump to page 2
doc.add_page
doc.save("links.pdf")
doc.close

Rectangles are [x0, y0, x1, y1] in points; page_index is 0-based.

Bookmarks / outline free

Build a navigable document outline. A Bookmark has a title, a target page and an optional top; nest children with .child(...). A document with bookmarks opens with the outline pane shown.

doc = RustPdf::Document.new
f = doc.add_font_file("Roboto-Regular.ttf")
3.times { doc.add_page }
doc.add_bookmark(
  RustPdf::Bookmark.new("Chapter 1", 0, top: 820)
    .child(RustPdf::Bookmark.new("Section 1.1", 1))
    .child(RustPdf::Bookmark.new("Section 1.2", 2)))
doc.add_bookmark(RustPdf::Bookmark.new("Chapter 2", 2))
doc.save("outline.pdf")
doc.close

Metadata

Sets the document information dictionary (and, for PDF/A, the matching XMP). Pass only the keywords you need.

doc.info(title: "Q3 Report", author: "Acme Inc.",
         subject: "Quarterly results", keywords: "finance, q3")

Manipulation: load an existing PDF

EditableDoc parses an existing document (classic & xref streams, object streams, all standard filters, RC4/AES decryption) into an editable model. Pages are a flat list; the page tree is rebuilt on output.

ed = RustPdf::EditableDoc.load_file("in.pdf")
puts ed.page_count
ed.close

# encrypted input:
sec = RustPdf::EditableDoc.load_file("secured.pdf", password: "user-or-owner-pw")
sec.save("plain.pdf")
sec.close

Pages: merge, split, reorder, rotate

a = RustPdf::EditableDoc.load_file("a.pdf")
b = RustPdf::EditableDoc.load_file("b.pdf")
a.merge(b)                          # a now has a's pages followed by b's
a.rotate_page(0, 90)
a.reorder_pages((0...a.page_count).to_a.reverse)
a.save("merged.pdf")
b.close

subset = a.extract_pages([0, 2])    # pages 1 and 3
subset.save("subset.pdf")
subset.close
a.close

Metadata, overlay & form fill

ed = RustPdf::EditableDoc.load_file("form.pdf")
ed.set_info("Title", "Filled form")
found = ed.fill_text_field("applicant.name", "Jane Doe")
puts "filled: #{found} | title: #{ed.get_info('Title')}"
ed.save("filled.pdf")
ed.close

Form fill & flatten free

Fill the fields of an existing AcroForm and (optionally) flatten them: filling generates a fresh appearance stream (no NeedAppearances), and flattening bakes every widget's appearance into the page content and removes the interactive form entirely.

ed = RustPdf::EditableDoc.load_file("form.pdf")
p ed.field_names                    # ["applicant.name", "agree", "plan", ...]
ed.fill_text_field("applicant.name", "Jane Doe")
ed.set_checkbox("agree", true)
ed.set_radio("billing", "annual")
ed.set_choice("plan", "Pro")
ed.flatten_forms                    # optional: make it non-editable
ed.save("filled.pdf")
ed.close

Watermarks free

Stamp a diagonal text watermark or a centered image watermark across every page, drawn semi-transparently over the existing content. Text uses the standard Helvetica font, so keep it to WinAnsi (Latin-1) for stamps like "CONFIDENTIAL".

ed = RustPdf::EditableDoc.load_file("report.pdf")
ed.watermark_text("CONFIDENTIAL", opacity: 0.25, rotation_deg: 45)
ed.save("stamped.pdf")
ed.close

Redaction licensed

True redaction: the text and graphics whose origin falls inside a rectangle are removed from the content stream (not just covered), so the data is gone from the file and is no longer extractable. Opaque black boxes are then painted over the regions.

ed = RustPdf::EditableDoc.load_file("statement.pdf")
# rects = array of [x0, y0, x1, y1] on that page
ed.redact(0, [[60, 590, 400, 620], [60, 540, 400, 570]])
ed.save("redacted.pdf")     # raises RustPdf::Error without a license granting redaction
ed.close

Convert to PDF/A licensed

Convert an existing PDF to archival PDF/A (a basic profile: A-1b, A-2b or A-3b). An sRGB output intent, PDF/A XMP metadata (synced with /Info) and a document /ID are added. Fails if any font is not embedded (PDF/A requires every font embedded) or a level-A profile is requested.

ed = RustPdf::EditableDoc.load_file("in.pdf")
ed.convert_to_pdfa(RustPdf::Pdfa::A2B)   # raises RustPdf::Error if fonts aren't embedded
ed.save("archival.pdf")                  # veraPDF: PDF/A-2b compliant
ed.close

Optimize & compact

ed = RustPdf::EditableDoc.load_file("big.pdf")
ed.optimize.compact(true)
ed.save("small.pdf")
ed.close

Encryption licensed

Apply standard-handler encryption at output. AES-256 (V5/R6) uses OS-CSPRNG keys/IVs.

ed = RustPdf::EditableDoc.load_file("in.pdf")
ed.encrypt(method: RustPdf::Cipher::AES256, owner: "owner-secret", read_only: true)
ed.save("secured.pdf")          # raises RustPdf::Error without an Encryption license
ed.close

See the Cipher enum for RC4 / AES-128 / AES-256.

Output & incremental update

original = File.binread("in.pdf")
ed = RustPdf::EditableDoc.load(original)
ed.set_info("Subject", "reviewed")
incremental = ed.to_bytes_incremental(original)   # original bytes preserved verbatim
File.binwrite("reviewed.pdf", incremental)
ed.close

Digital signatures licensed

Sign a PDF with a PKCS#7 detached signature via an incremental update (the original bytes are preserved). Keys and certificates are passed as DER byte Strings. pades: true switches to PAdES-B-B.

pdf      = File.binread("contract.pdf")
key_der  = File.binread("signing-key.pkcs8.der")   # PKCS#8 private key (DER)
cert_der = File.binread("signing-cert.der")        # X.509 certificate (DER)

signed = RustPdf.sign(pdf, key_der, cert_der,
                      reason: "Approved", location: "New York",
                      name: "Jane Doe", pades: true)
File.binwrite("contract.signed.pdf", signed)
# Verify in a shell: pdfsig contract.signed.pdf  →  "Signature is Valid."

Timestamp & DSS (PAdES LTV) licensed

Build long-term-validation signatures offline. add_dss appends a Document Security Store (/DSS with certs/CRLs, PAdES-B-LT); timestamp appends an RFC 3161 document timestamp (/DocTimeStamp, PAdES-B-LTA).

signed = File.binread("contract.signed.pdf")

# B-LT: embed validation material (caller supplies DER certs/CRLs)
lt = RustPdf.add_dss(signed, certs: [cert_der], crls: [crl_der])

# B-LTA: add a document timestamp signed by a TSA key/cert
lta = RustPdf.timestamp(lt, tsa_key_der, tsa_cert_der)
File.binwrite("contract.lta.pdf", lta)

Validate signatures licensed

Validate every signature in a PDF: each report recomputes the /ByteRange digest, parses the CMS, and checks that the cryptographic signature is valid, that the messageDigest matches the covered bytes, and whether the signature covers the whole document.

Each entry is a Hash with keys "field_name" and "signer" (both nil when absent), plus "sub_filter", "covers_whole_document", "digest_valid", "signature_valid", "is_valid" and "byte_range". An empty array means the document is unsigned. Signature validation is a licensed feature: this call requires an active license (signatures) even when the document is unsigned — it is not available on the free tier.

data = File.binread("contract.signed.pdf")
RustPdf.verify_signatures(data).each do |sig|
  puts "#{sig['signer']} valid: #{sig['is_valid']} " \
       "covers whole doc: #{sig['covers_whole_document']}"
end

Text & image extraction

Extract a document's text, mapping shown glyph codes back to Unicode through each font's ToUnicode map, with space/line inference. Raster images can be pulled out too: JPEGs are written verbatim as .jpg, everything else as .png. The output directory is created automatically if it does not already exist.

data = File.binread("report.pdf")
puts RustPdf.extract_text(data)

n = RustPdf.extract_images_to_dir(data, "out_images/")   # returns how many were written
puts "wrote #{n} image(s)"

Render a page to an image licensed

Rasterize a page to a PNG image. A native Rust renderer (built on tiny-skia, with no headless browser) interprets the page content stream, painting real glyph outlines, vector graphics, images, color and transparency. Page rendering is a Pro feature; page_count is free.

data = File.binread("report.pdf")
puts "#{RustPdf.page_count(data)} page(s)"
File.binwrite("page1.png", RustPdf.render_page_to_png(data, 0, 150.0))

Enums

Pdfa

Align

Relationship

Cipher

FacturxProfile

Error handling

Every failing native call raises RustPdf::Error (a StandardError) carrying the status (PdfStatus) code and the library's last-error message. License failures (missing/expired/forged token, or a feature the token doesn't grant) surface here too. Token activation failures carry the dedicated license status code (12); a gated build, sign or encrypt call instead reports that operation’s own status (for example Serialize = 4 or Sign = 10) with the same “requires a valid license” message.

begin
  doc = RustPdf::Document.new
  doc.pdfa.info(title: "x")
  doc.add_page
  doc.save("out.pdf")
  doc.close
rescue RustPdf::Error => e
  warn "failed: #{e.status} #{e.message}"
  # e.g. PdfStatus=4 (Serialize): feature 'pdfa' requires a valid license
end

Utilities