How do you combine PDFs in ruby?

Question

This was asked in 2008. Hopefully there's a better answer now.

How can you combine PDFs in ruby?

I'm using the pdf-stamper gem to fill out a form in a PDF. I'd like to take n PDFs, fill out a form in each of them, and save the result as an n-page document.

Can you do this with a native library like prawn? Can you do this with rjb and iText? pdf-stamper is a wrapper on iText.

I'd like to avoid using two libraries (i.e. pdftk and iText), if possible.

Answer 1

We're closer than we were in 2008, but not quite there yet.

The latest dev version of Prawn lets you use an existing PDF as a template, but not use a template over and over as you add more pages.

Answer 2

Via iText, this will work... though you should flatten the forms before you merge them to avoid field name conflicts. That or rename the fields one page at a time.

Within PDF, fields with the same name share a value. This is usually not the desired behavior, though it comes in handy from time to time.

Something along the lines of (in java):

PdfCopy mergedPDF = new PdfCopy( new Document(), new FileOutputStream( outPath );

for (String path : paths ) {
  PdfReader reader = new PdfReader( path );
  ByteArrayOutputStream curFormOut = new ByteArrayOutputStream();
  PdfStamper stamper = new PdfStamper( reader, curFormOut );

  stamper.setField( name, value ); // ad nauseum

  stamper.setFlattening(true); // flattening setting only takes effect during close()
  stamper.close();

  byte curFormBytes = curFormOut.toByteArray();
  PdfReader combineMe = new PdfReader( curFormBytes );

  int pages = combineMe .getNumberOfPages();
  for (int i = 1; i <= pages; ++i) { // "1" is the first page
    mergedForms.addPage( mergedForms.getImportedPage( combineMe, i );
  }
}

mergedForms.close();

Answer 3

I wrote a ruby gem to do this — PDF::Merger. It uses iText. Here's how you use it:

pdf = PDF::Merger.new
pdf.add_file "foo.pdf"
pdf.add_file "bar.pdf"
pdf.save_as "combined.pdf"