using foxit;
using foxit.common;
using foxit.common.fxcrt;
using foxit.pdf;
using foxit.pdf.annots;
using foxit.addon;
...

using (PDFDoc base_doc = new PDFDoc("input_base_file"))
{
 error_code = base_doc.Load(null);
 if (error_code != ErrorCode.e_ErrSuccess)
 {
 Library.Release();
 return;
 }

 using (PDFDoc compared_doc = new PDFDoc("input_compared_file"))
 {
 error_code = compared_doc.Load(null);
 if (error_code != ErrorCode.e_ErrSuccess)
 {
 Library.Release();
 return;
 }

 using (Comparison comparison = new Comparison(base_doc, compared_doc))
 {
 // Start comparing.
 CompareResults result = comparison.DoCompare(0, 0, (int)Comparison.CompareType.e_CompareTypeText);
 CompareResultInfoArray oldInfo = result.results_base_doc;
 CompareResultInfoArray newInfo = result.results_compared_doc;
 uint oldInfoSize = oldInfo.GetSize();
 uint newInfoSize = newInfo.GetSize();

 using (PDFPage page = compared_doc.GetPage(0))
 {
 for (uint i = 0; i < newInfoSize; i++)
 {
 CompareResultInfo item = newInfo.GetAt(i);
 CompareResultInfo.CompareResultType type = item.type;
 if (type == CompareResultInfo.CompareResultType.e_CompareResultTypeDeleteText)
 {
 String res_string = String.Format(""{0}"", item.diff_contents);

 // Add stamp to mark the "delete" type differences between the two documents.
 CreateDeleteTextStamp(page, item.rect_array, 0xff0000, res_string, "Compare : Delete", "Text");
 }
 else if (type == CompareResultInfo.CompareResultType.e_CompareResultTypeInsertText)
 {
 String res_string = String.Format(""{0}"", item.diff_contents);

 // Highlight the "insert" type differences between the two documents.
 CreateHighlightRect(page, item.rect_array, 0x0000ff, res_string, "Compare : Insert", "Text");
 }
 else if (type == CompareResultInfo.CompareResultType.e_CompareResultTypeReplaceText)
 {
 String res_string = String.Format("[Old]: "{0}"rn[New]: "{1}"", oldInfo.GetAt(i).diff_contents, item.diff_contents);

 // Highlight the "replace" type differences between the two documents.
 CreateHighlightRect(page, item.rect_array, 0xe7651a, res_string, "Compare : Replace", "Text");
 }
 }
 }

 // Save the comparison result to a PDF file.
 compared_doc.SaveAs(output_path + "result.pdf", (int)PDFDoc.SaveFlags.e_SaveFlagNormal);
 }
 }
}