Annotation overview

Foxit PDF SDK for iOS supports most PDF annotation types via Core SDK for create, property access, appearance generation, and rendering.

UI Extensions built-in annotations

With the full reader (UI Extensions), common annotations (highlight, note, drawing, stamp, etc.) are available from the toolbar. This guide focuses on programmatic control.

Annotation types

PDF annotation types, Markup classification, and SDK support:

Type	Constant	Description	Markup	SDK support
Text (Note)	FSAnnotNote	Note / text comment	Yes	Supported
Link	FSAnnotLink	Hyperlink	No	Supported
FreeText	FSAnnotFreeText	Free text (typewriter / text box / callout)	Yes	Supported
Line	FSAnnotLine	Line / arrow	Yes	Supported
Square	FSAnnotSquare	Rectangle	Yes	Supported
Circle	FSAnnotCircle	Circle / ellipse	Yes	Supported
Polygon	FSAnnotPolygon	Polygon	Yes	Supported
PolyLine	FSAnnotPolyLine	Polyline	Yes	Supported
Highlight	FSAnnotHighlight	Text highlight	Yes	Supported
Underline	FSAnnotUnderline	Underline	Yes	Supported
Squiggly	FSAnnotSquiggly	Squiggly underline	Yes	Supported
StrikeOut	FSAnnotStrikeOut	Strikethrough	Yes	Supported
Stamp	FSAnnotStamp	Stamp	Yes	Supported
Caret	FSAnnotCaret	Caret	Yes	Supported
Ink	FSAnnotInk	Freehand ink	Yes	Supported
Popup	FSAnnotPopup	Popup for comment text	No	Supported
FileAttachment	FSAnnotFileAttachment	File attachment	Yes	Supported
Sound	FSAnnotSound	Sound	Yes	Not supported
Movie	FSAnnotMovie	Movie	No	Not supported
Widget	FSAnnotWidget	Form widget	No	Supported
Screen	FSAnnotScreen	Screen / media	No	Supported
PrinterMark	FSAnnotPrinterMark	Printer mark	No	Not supported
TrapNet	FSAnnotTrapNet	Trap net	No	Not supported
Watermark	FSAnnotWatermark	Watermark annotation	No	Not supported
3D	FSAnnot3D	3D	No	Not supported
Redact	FSAnnotRedact	Redaction	Yes	Supported

INFO

The SDK also supports custom type PSI (Pressure Sensitive Ink, FSAnnotPSInk), not defined in the PDF spec—typically for handwriting.

The PDF Watermark annotation type is not supported; page-content watermarks are supported. See Watermarks.

Class hierarchy

FSAnnot                   ← Base class
├── FSMarkup              ← Markup base (title, subject, opacity, replies, grouping, etc.)
│   ├── FSTextMarkup      ← Text markup (Highlight / Underline / StrikeOut / Squiggly)
│   ├── FSFreeText        ← Free text
│   ├── FSNote            ← Note
│   ├── FSLine            ← Line
│   ├── FSSquare          ← Square
│   ├── FSCircle          ← Circle
│   ├── FSInk             ← Ink
│   ├── FSStamp           ← Stamp
│   ├── FSCaret           ← Caret
│   ├── FSFileAttachment  ← File attachment
│   └── FSRedact          ← Redaction
├── FSLink                ← Link
├── FSScreen              ← Screen
├── FSWidget              ← Widget
└── FSPopup               ← Popup

FSAnnot — common properties

Method	Description
getType	Annotation type (FSAnnotType)
getPage	Page
getRect / setRect:	Bounding rect
move:	Move
getContent / setContent:	Text content
getBorderColor / setBorderColor:	Border color
getBorderInfo / setBorderInfo:	Border (width, style, dash)
getFlags / setFlags:	Flags (hidden, locked, etc.)
getUniqueID / setUniqueID:	Unique ID
getModifiedDateTime / setModifiedDateTime:	Modified time
resetAppearanceStream	Regenerate appearance (required after property changes)
isEmpty	Empty check

Important

After changing properties, call resetAppearanceStream so appearance updates apply.

FSMarkup — extended properties

Method	Description
getTitle / setTitle:	Author / title
getSubject / setSubject:	Subject
getOpacity / setOpacity:	Opacity (0.0–1.0)
getIntent / setIntent:	Intent (e.g. FreeText subtypes)
getCreationDateTime / setCreationDateTime:	Creation time
getPopup / setPopup:	Associated popup
getReplyCount	Reply count
getReply: / addReply / removeReply:	Replies (FSNote)
removeAllReplies	Remove all replies
isGrouped	In a group
getGroupHeader / getGroupElements / ungroup	Grouping
getStateAnnots: / addStateAnnot:stateModel:state:	Review / mark states

Create annotations

Use [FSPDFPage addAnnot:rect:]:

#import <FoxitRDK/FSPDFObjC.h>

FSPDFDoc *doc = [[FSPDFDoc alloc] initWithPath:@"path/to/Sample.pdf"];
[doc load:nil];
FSPDFPage *page = [doc getPage:0];

FSRectF *rect = [[FSRectF alloc] initWithLeft1:100 bottom1:100 right1:130 top1:130];
FSAnnot *annot = [page addAnnot:FSAnnotNote rect:rect];
FSNote *note = [[FSNote alloc] initWithAnnot:annot];

[note setIconName:@"Comment"];
[note setBorderColor:0xFF0000FF];
[note setContent:@"This is a note annotation."];

[note resetAppearanceStream];

[doc saveAs:@"path/to/output.pdf" saveFlags:FSPDFDocSaveFlagNormal];

Remove annotations

FSAnnot *annot = [page getAnnot:0];
if (annot && ![annot isEmpty]) {
    [page removeAnnot:annot];
}

Annotation events

Register IAnnotEventListener on UIExtensionsManager:

[extensionsManager registerAnnotEventListener:self];

// IAnnotEventListener
- (void)onAnnotAdded:(FSPDFPage *)page annot:(FSAnnot *)annot {
    NSLog(@"Annotation added: %@", [annot getContent]);
}

- (void)onAnnotDeleted:(FSPDFPage *)page annot:(FSAnnot *)annot {
    NSLog(@"Annotation deleted");
}

- (void)onAnnotModified:(FSPDFPage *)page annot:(FSAnnot *)annot {
    NSLog(@"Annotation modified");
}

Note

Unregister with unregisterAnnotEventListener: when the view controller is torn down to avoid leaks.

More annotation topics

• Text markup — Highlight, underline, strikethrough, squiggly
• Notes and free text — Note, typewriter, text box, callout, caret
• Shapes and drawing — Line, square, circle, polygon, polyline, ink
• Stamps — Standard and custom stamps
• Links — URI and in-document links
• Redaction — Create and apply redactions
• Import and export — FDF/XFDF, flatten

API reference

See the API reference for FSAnnot, FSMarkup, FSNote, FSLine, FSTextMarkup, and related classes.