Appendix A — Glossary

Annotation Any markup object on a PDF page: highlight, shape, text box, stamp, measurement, redaction, etc.

AcroForm The interactive form model used in most PDFs — text fields, checkboxes, radio buttons, etc. Spark fills AcroForm fields in place.

Bounding Box The smallest axis-aligned rectangle that contains a shape. Used for resize handles, hit testing and alignment.

Calibration Setting the conversion between on-page points and real-world units for a document so measurement tools produce meaningful values.

Canvas The WPF drawing surface inside a document pane where the PDF page and its annotations are rendered.

Cloud / Revision Cloud A scalloped outline indicating a changed or noteworthy region on a drawing.

Cloud Intensity The size of the arc "bumps" on a cloud annotation. Larger = tighter bumps.

Cloud Orientation Whether cloud bumps point outward (classic) or inward (cut-out).

Continuous Mode A view mode where all pages flow in a scrollable vertical stack. See 02.1.

Context Menu The menu that appears when right-clicking. Different annotations / empty canvas / thumbnails have different menus.

Count Marker A tally-point annotation used for counting items; part of the Measurement tools.

Document Pane A region that renders a PDF. Split view divides the pane into multiple independent regions.

Drawing Tool A tool that creates a new annotation (Rectangle, Circle, Text Box, Stamp, etc.). Contrast with Select Tool.

FDF / XFDF Form Data Format / XML Form Data Format — exchange formats for form field values.

Flatten Convert editable elements (form fields, annotations) into baked-in visible content that cannot be edited separately.

Form Field An interactive PDF element (text input, checkbox, dropdown, signature pad). Separate from annotations.

Group (annotation) A set of annotations linked by a shared Group ID so they transform and delete together.

Handle A small on-screen marker for interactive transformation — corner handles (resize), rotation handle (rotate), vertex handle (per-point edit), central move handle.

Highlight Form Fields A view toggle that overlays a pale color on every AcroForm field so you can spot them.

Layer / OCG Optional Content Group — a PDF layer containing a subset of content that can be shown or hidden independently.

Markup Informal term for reviewer annotations (highlights, clouds, sticky notes, callouts).

Measurement An annotation that computes and displays a real-world dimension based on calibrated scale.

OCR Optical Character Recognition — detecting text in image-based pages and adding an invisible text layer.

Page-Relative Coordinates Storage format for annotation positions, measured in the original PDF's page coordinate system, independent of zoom or display rotation.

PDF / A A strict archival subset of PDF; used for long-term preservation.

Persistent ID A GUID attached to each annotation so it can be uniquely referenced across save / open cycles.

Polygon / Polyline Polyline is an open multi-point path; Polygon is closed. Both are drawn with click-to-add-vertex and double-click-to-finish.

Redaction Marking and then permanently removing sensitive content from a PDF. Two stages: mark (reversible) and apply (permanent).

Select Tool The cursor mode for editing existing annotations. Keyboard shortcut V or Esc.

Shape Annotation Any of the 30+ predefined geometric shapes (Rectangle, Star, Hexagon, Chevron, etc.).

Signature (visual) A drawn or imported image annotation. Contrast with digital (cryptographic) signature.

Signature (digital) A cryptographic signature tied to a certificate, verifiable for authenticity.

Split View Dividing the document pane into 2 or 4 independent regions. Each region has its own page, zoom and view mode.

Stamp A pre-built or custom image / text marker (Approved, Draft, etc.) placed on a page.

Sticky Note A compact annotation shown as an icon that expands into a text popup. For short comments.

Text Box A rectangular annotation with editable formatted text content, always visible on the page.

Text Callout A text box with a leader line pointing at a specific location.

Text Markup Highlight, Underline, Strikethrough, Squiggly — annotations that decorate existing selectable text.

Thumbnail A miniature page preview in the left panel.

Tool Options A panel or popup showing settings for the active tool (color, stroke, style).

Undo Entry One atomic change recorded in the undo stack. Ctrl+Z reverts one entry at a time.

Vertex Handle A small orange dot drawn at each vertex of a selected polygon / polyline / freehand; drag to move one point.

View Rotation Rotating the display without changing the PDF. Different from Page Rotation.

Z-order The stacking order of annotations on a page. Bring to Front / Send to Back changes it.

Zoom-Aware A rendering mode where handles and line widths scale with zoom so they stay visually consistent.