Export annotations on iOS

To extract data from PDF to FDF, then export FDF as XFDF

PTPDFDoc *doc = [[PTPDFDoc alloc] initWithFilepath: filename];

// Extract annotations to FDF.
// Optionally use e_ptboth to extract both forms and annotations
PTFDFDoc *doc_fields = [doc FDFExtract: e_ptannots_only]; //e_ptforms_only

// Export annotations from FDF to XFDF.
[doc_fields SaveAsXFDF: output_xfdf_filename];

// Optionally write XFDF to a string
NSString *XFDF_string = [doc_fields SaveAsXFDFToString];

PDF Form Fill and Form Data Extraction
Full sample code which illustrates basic FDF merge/extract functionality and full support for FDF (Forms Data Format)