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How To Add Auto Text To PDF Documents

Learn to use placeholders in PDFtoolkit text outs on PDF pages.

By V. Subhash

If you have used word-processing software such as Microsoft Word, you may be familiar with the concept of "auto text." PDFtoolkit brings the same functionality to PDF by supporting placeholders in PDF page text-outs. You can use placeholders with TgtTextWatermarkTemplate class and the TgtDFDocument.TextOut method. PDFtoolkit comes with the following built-in placeholders.

Placeholder	Substituted By
PageNo	Number of current page
TotPage	Total number of pages
ShortDate	Date in short format
ShortTime	Time in short format
LongDate	Date in long format
LongTime	Date in long format
Author	Document author property (See TgtPDFDocument.DocInfo)
Creator	Document creator property (See TgtPDFDocument.DocInfo)
Subject	Document subject property (See TgtPDFDocument.DocInfo)
Title	Document title property (See TgtPDFDocument.DocInfo)

PDFtoolkit also supports custom or user-defined placeholders. Your application can provide values for custom placeholders by handling the TgtPDFDocument.OnCalcVariables event.

Both built-in and custom placeholders need to be delimited by <% and %>. When the output document is being paged, the placeholders will be replace with their values available at run time. Here is an example.

{
 This code example illustrates how to write text
 watermarks to a document. It also illustrates the
 use of autotext placeholders.
}
program Examples_Autotext;

{$APPTYPE CONSOLE}

uses
  SysUtils,
  gtPDFDoc, gtCstPDFDoc;

var
  gtPDFDocument1: TgtPDFDocument;
  gtTextWatermarkTemplate1: TgtTextWatermarkTemplate;
begin
  // Create a document object
  gtPDFDocument1 := TgtPDFDocument.Create(Nil);
  gtTextWatermarkTemplate1 := TgtTextWatermarkTemplate.Create();

  try
    // Load input document
    gtPDFDocument1.LoadFromFile('input_doc.pdf');

    // Check if document has loaded successfully
    if gtPDFDocument1.IsLoaded then
     begin

      // Set watermark properties
      With gtTextWatermarkTemplate1 do
      begin
        Font.Name := 'Courier New';
        Font.Size := 8;
        Text := 'Autotext example [PageNo - <%PageNo%>, TotPage - <%TotPage%>, '
                   + 'ShortDate - <%ShortDate%>, Author - <%Author%>]';
        Overlay := false;      // Underlay
        OpacityStroke := 100;  // Full opaqueness
        HorizPos := hpCenter;  // Relative positioning
        VertPos := vpCustom;   // Absolute positioning
        Y := 10;               // Absolute vertical position
      end;      
      
      // Apply the watermark on all pages
      gtPDFDocument1.InsertWatermark(gtTextWatermarkTemplate1);

      // Save modified document
      gtPDFDocument1.SaveToFile('output_doc.pdf');

     end
    else
     begin
      // Output error message
      Writeln('Sorry, I could not load input_doc.pdf.');
     end;
  except on Err:Exception do
   begin
     Writeln('Sorry, an exception was raised. ');
     Writeln(Err.Classname + ':' + Err.Message);
   end;
  end;
  // Free resources
  gtPDFDocument1.Reset;
  // Destroy PDF document object
  FreeAndNil(gtPDFDocument1);

  Writeln('Press Enter to exit.');
  Readln;
end.

And, here is the output.

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