PDF Specification Reference

Begin Text Object

Begins a text object, initializing the text matrix and line matrix to the identity matrix. Must be paired with ET.

End Text Object

Ends a text object, discarding the text matrix. All text output must occur between BT and ET.

Set Character Spacing

Sets the character spacing to charSpace, in unscaled text space units. Added between consecutive characters in a string.

Set Word Spacing

Sets the word spacing to wordSpace (applied to ASCII space character, 0x20).

Set Horizontal Scaling

Sets the horizontal scaling to scale percent (100 = normal; 50 = half-width; 200 = double-width).

Set Text Leading

Sets the text leading (line spacing) used by the T*, quote, and double-quote operators.

Set Font and Size

Sets the text font to font (a resource name) and the text font size to size.

Set Text Rendering Mode

Sets the text rendering mode: 0=fill, 1=stroke, 2=fill+stroke, 3=invisible, 4=fill+clip, 5=stroke+clip, 6=fill+stroke+clip, 7=clip only.

Set Text Rise

Sets the text rise to rise, moving the baseline up or down. Positive values move text up (superscript); negative values move text down (subscript).

Move Text Position

Moves to the start of the next line, offset by (tx, ty) from the start of the current line.

Move Text Position and Set Leading

Moves to the start of the next line, offset by (tx, ty), and also sets the text leading to -ty. Equivalent to -ty TL followed by tx ty Td.

Set Text Matrix

Sets the text matrix and text line matrix to the given 6-element matrix. Used to position and transform text freely.

Move to Next Line

Moves to the start of the next text line. Equivalent to 0 -TL Td where TL is the current text leading value.

Show Text String

Shows a text string at the current text position, applying glyph widths from the current font.

Show Text with Kerning

Shows one or more strings, allowing individual glyph positioning via kerning values. Numeric array elements adjust the horizontal position between strings.

Move to Next Line and Show Text

Moves to the next line and shows a text string. Equivalent to T* followed by (string) Tj.

Set Spacing, Move, and Show Text

Sets word and character spacing, moves to the next text line, and shows the string.

Move To

Begins a new subpath by moving the current point to (x, y). Implicitly closes any previous path and starts a new one.

Line To

Appends a straight line segment from the current point to (x, y), making (x, y) the new current point.

Cubic Bezier Curve (full)

Appends a cubic Bézier curve using two control points (x1,y1), (x2,y2) and endpoint (x3,y3). Commonly used for smooth curves.

Cubic Bezier Curve (initial current point)

Appends a cubic Bézier curve where the first control point coincides with the current point.

Cubic Bezier Curve (final control)

Appends a cubic Bézier curve where the second control point coincides with the endpoint (x3,y3).

Close Path

Closes the current subpath by appending a straight line from the current point back to the starting point of the subpath.

Append Rectangle

Appends a complete rectangle to the current path as a closed subpath. Equivalent to m, three l operations, and h.

Stroke Path

Strokes the current path using the current stroke color and line width settings. Path is then cleared from current path.

Close and Stroke

Closes the current subpath (as if h were applied) then strokes it. Equivalent to h S.

Fill Path (nonzero)

Fills the path using the nonzero winding number rule. Any open subpaths are implicitly closed before filling.

Fill Path (even-odd)

Fills the path using the even-odd rule. Useful for shapes with holes or self-intersections.

Fill and Stroke

Fills then strokes the path using the nonzero winding rule.

Fill (even-odd) and Stroke

Fills (using even-odd rule) then strokes the path.

Close, Fill and Stroke

Closes, fills (nonzero), and strokes the path. Equivalent to h B.

Close, Fill (even-odd) and Stroke

Closes, fills (even-odd), and strokes the path. Equivalent to h B*.

End Path (no paint)

Ends the current path without filling or stroking. Used to apply clipping or discard a path silently.

Set Stroke Color Space

Sets the current stroke color space to the named color space (/DeviceRGB, /DeviceCMYK, /DeviceGray, or a resource name).

Set Fill Color Space

Sets the current fill (non-stroking) color space to the named color space.

Set Stroke Color

Sets the stroke color using the current color space. Number of arguments depends on the color space (1 for gray, 3 for RGB, 4 for CMYK).

Set Fill Color

Sets the fill color using the current color space.

Set Stroke Color (extended)

Extended version of SC that also supports Pattern, Separation, DeviceN, and ICCBased color spaces. Optional pattern name argument.

Set Fill Color (extended)

Extended version of sc that also supports Pattern, Separation, DeviceN, and ICCBased color spaces.

Set Gray Stroke

Sets the stroke color space to DeviceGray and the gray value (0 = black, 1 = white).

Set Gray Fill

Sets the fill color space to DeviceGray and the gray value.

Set RGB Stroke

Sets the stroke color space to DeviceRGB and the RGB components (0-1 range each).

Set RGB Fill

Sets the fill color space to DeviceRGB and the RGB components.

Set CMYK Stroke

Sets the stroke color space to DeviceCMYK and the CMYK components (0-1 range each).

Set CMYK Fill

Sets the fill color space to DeviceCMYK and the CMYK components.

Clip Path (nonzero)

Modifies the current clipping path by intersecting it with the current path, using the nonzero winding rule. Must precede a path-painting operator (f, S, n, etc.).

Clip Path (even-odd)

Same as W but uses the even-odd rule for determining the inside of the path.

Save Graphics State

Pushes a copy of the current graphics state onto the graphics state stack. Use with Q to sandbox state changes.

Restore Graphics State

Pops the graphics state stack, restoring the state saved by the most recent q operator.

Set Line Width

Sets the line width in user space units. Applies to all subsequent stroke operations until changed.

Set Line Cap Style

Sets the line cap style: 0 = butt cap, 1 = round cap, 2 = projecting square cap.

Set Line Join Style

Sets the line join style: 0 = miter join, 1 = round join, 2 = bevel join.

Set Miter Limit

Sets the maximum length of mitered line joins. When the miter length exceeds miterLimit × line width, the join is beveled.

Set Dash Pattern

Sets the line dash pattern for stroked paths. dashArray is an array of dash and gap lengths; dashPhase is the offset into the pattern.

Set Color Rendering Intent

Sets the color rendering intent: /AbsoluteColorimetric, /RelativeColorimetric, /Saturation, or /Perceptual.

Set Flatness Tolerance

Sets the flatness tolerance, controlling the maximum approximation error for curved paths. 0 means device-dependent default.

Set Graphics State Parameters

Sets multiple graphics state parameters from an ExtGState resource dictionary, enabling access to parameters not settable by dedicated operators.

Concatenate Matrix

Modifies the current transformation matrix (CTM) by concatenating the given 6-element matrix [a b c d e f]. Used for translation, scaling, rotation, and skewing.

PDF Header

Every PDF file must begin with this comment-style header identifying the PDF version (e.g., %PDF-1.7 or %PDF-2.0). A binary hint comment with 4 bytes ≥128 is recommended after this header.

Trailer Dictionary

Marks the end of a PDF file. Contains the startxref value (byte offset of the last cross-reference table), the trailer dictionary (/Root, /Info, /Size, /Encrypt, /ID), and the %%EOF end-of-file marker.

Cross-Reference Table

Maps each indirect object number to its byte offset in the file, enabling random access. An xref stream (PDF 1.5+) can replace the traditional text-based table for compression.

/Catalog Dictionary

The root object of a PDF document, referenced from the trailer /Root key. Contains required /Pages reference plus optional entries: /Outlines, /Names, /OpenAction, /AcroForm, /Lang, /MarkInfo, /ViewerPreferences, /OCProperties.

/Pages Dictionary

Intermediate node in the page tree. /Kids lists direct children (page or pages nodes); /Count is the total leaf page count in the subtree.

/Page Dictionary

Represents a single page. Required: /Type /Page, /Parent (reference to /Pages node), /MediaBox (page bounding box in points). Common optional keys: /CropBox, /BleedBox, /TrimBox, /ArtBox, /Rotate, /Resources, /Contents, /Annots, /Tabs, /StructParents.

/Encrypt Dictionary

Present in the trailer when a PDF is encrypted. /Filter names the security handler (/Standard for password-based encryption). /V specifies the algorithm version; /R the revision; /O and /U are hashed owner and user passwords; /P is the permissions bitmask.

/P Permissions Bitmask

Bit flags in the /Encrypt /P entry control user permissions. Bit 3 (print), Bit 4 (modify), Bit 5 (copy), Bit 6 (add/modify annotations), Bit 9 (fill forms), Bit 10 (extract for accessibility), Bit 11 (assemble), Bit 12 (high-quality print). Bits not set deny the permission.

/Type1 Font

Adobe Type 1 PostScript font. 14 standard fonts (Helvetica, Times-Roman, Courier, Symbol, ZapfDingbats, and bold/italic variants) are guaranteed present in PDF viewers without embedding. All others must be embedded.

/TrueType Font

TrueType font (TTF). Must include /Widths, /FirstChar, /LastChar, and /Encoding for proper text extraction. Embedding recommended for portability.

/Type0 (Composite) Font

Composite font supporting Unicode and large character sets. Used for CJK and full Unicode text. Requires a CIDFont descendant (/CIDFontType0 or /CIDFontType2) and a CMap for encoding.

/OpenType Font

OpenType fonts (OTF) are embedded as either CFF (use /Type1 subtype) or TrueType-outlines (use /TrueType subtype) wrapped in an OTF container. PDF 1.6+ supports OpenType directly as /Subtype /OpenType in a font file stream.

/ToUnicode CMap Stream

A CMap stream embedded in a font dictionary that maps character codes to Unicode values. Required for reliable text extraction and copy-paste from PDF. Without this, text extraction is best-effort.

/AcroForm Dictionary

The interactive form root dictionary stored in /Catalog. /Fields lists top-level form field references; /DR is the default resources dictionary; /DA is the default appearance string. /NeedAppearances true tells viewers to reconstruct appearance streams.

/Widget Annotation (Form Field)

Represents a visible form field on a page. /FT specifies the field type: /Tx (text input), /Btn (button/checkbox/radio), /Ch (choice/dropdown/listbox), /Sig (signature). /T is the partial field name; the full name is the dot-joined path from the root.

/Group (Transparency)

Defines a transparency group on a page or form XObject. /CS sets the group color space; /I (Isolated, default false) determines if the group composites over a white background; /K (Knockout, default false) enables knockout group compositing.

/SMask (Soft Mask)

Defines a soft mask (alpha channel equivalent) for use with compositing. /S /Luminosity uses luminosity values as the mask; /S /Alpha uses alpha channel values. Attached to an ExtGState resource.

/OCG (Optional Content Group)

Defines a named layer (Optional Content Group). Marked content tagged with /OC pointing to an OCG can be shown or hidden without altering the PDF content stream. Used in engineering drawings, multilingual documents, and print vs. screen variants.

/OCProperties Dictionary

Stored in the document /Catalog. /OCGs lists all OCG references; /D is the default configuration (which layers are on by default, the base state, viewing intent, etc.); /Configs holds alternate configurations.

/Info Dictionary

Traditional document metadata dictionary, referenced from the trailer. All entries are optional text strings. Superseded by XMP metadata streams in PDF 1.4+ but still widely supported.

/Metadata (XMP) Stream

Embedded XMP (Extensible Metadata Platform) metadata in an XML stream. Stores richer metadata than /Info including Dublin Core, IPTC, GPS, rights management, and custom schemas. Referenced from /Catalog /Metadata or resource dictionaries.

/MarkInfo Dictionary

Stored in /Catalog. /Marked true declares the PDF as a tagged PDF with logical structure. /Suspects true means some tagged content may be incorrectly tagged. PDF/UA-1 requires /Marked true.

/StructTreeRoot

Root of the document logical structure tree. /K contains direct children (structure elements); /ParentTree maps MCID values to parent structure elements for reverse lookup; /RoleMap maps custom tag names to standard PDF tag types.

Structure Element Types

Standard PDF structure element types defined in ISO 32000. These tags form the logical reading order tree. /P is a paragraph; /H1-H6 are headings; /Figure requires an /Alt attribute for accessibility; /Table requires header association for PDF/UA.

Paint Shading Pattern

Paints the area defined by the current clipping path using the named shading pattern from the Shading resources.

Invoke XObject

Invokes a named XObject (image, form XObject, or PostScript XObject) from the page resources. The XObject is positioned using the current CTM.

Begin Inline Image

Begins an inline image object. The image dictionary entries follow BI, then ID begins the image data, and EI ends the inline image.

/Sig (Signature Field)

A signature form field. The /V entry references a signature dictionary containing the signature value, SubFilter (handler name), ByteRange (byte ranges covered), Contents (DER-encoded PKCS#7 or CMS blob), and optional /Reason, /Location, /ContactInfo.

/DocMDP (Document Modification Detection)

A certification signature permission level. /P 1 = no changes permitted after signing; /P 2 = form filling and signing permitted; /P 3 = annotations and form filling permitted. Applied via the /DocMDP transform method in the /Reference array of a signature dictionary.

Begin Marked Content

Begins a marked-content sequence with the given tag name. Paired with EMC. Used for tagged PDF structure.

Begin Marked Content (with dict)

Begins a marked-content sequence with a tag and associated properties dictionary or resource name.

End Marked Content

Ends a marked-content sequence started by BMC or BDC.

Designate Marked Content Point

Designates a marked-content point (not a sequence) with the given tag.

Designate Marked Content Point (with dict)

Designates a marked-content point with a tag and associated properties dictionary or resource name.