How do you combine PDFs in ruby? - 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

As of 2013 you can use Prawn to merge pdfs. Gist: https://gist.github.com/4512859
class PdfMerger
def merge(pdf_paths, destination)
first_pdf_path = pdf_paths.delete_at(0)
Prawn::Document.generate(destination, :template => first_pdf_path) do |pdf|
pdf_paths.each do |pdf_path|
pdf.go_to_page(pdf.page_count)
template_page_count = count_pdf_pages(pdf_path)
(1..template_page_count).each do |template_page_number|
pdf.start_new_page(:template => pdf_path, :template_page => template_page_number)
end
end
end
end
private
def count_pdf_pages(pdf_file_path)
pdf = Prawn::Document.new(:template => pdf_file_path)
pdf.page_count
end
end

Answer 2

After a long search for a pure Ruby solution, I ended up writing code from scratch to parse and combine/merge PDF files.
(I feel it is such a mess with the current tools - I wanted something native but they all seem to have different issues and dependencies... even Prawn dropped the template support they use to have)
I posted the gem online and you can find it at GitHub as well.
you can install it with:
gem install combine_pdf
It's very easy to use (with or without saving the PDF data to a file).
For example, here is a "one-liner":
(CombinePDF.load("file1.pdf") << CombinePDF.load("file2.pdf") << CombinePDF.load("file3.pdf")).save("out.pdf")
If you find any issues, please let me know and I will work on a fix.

Answer 3

Use ghostscript to combine PDFs:
options = "-q -dNOPAUSE -dBATCH -sDEVICE=pdfwrite"
system "gs #{options} -sOutputFile=result.pdf file1.pdf file2.pdf"

Answer 4

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"

Answer 5

Haven't seen great options in Ruby- I got best results shelling out to pdftk:
system "pdftk #{file_1} multistamp #{file_2} output #{file_combined}"

Answer 6

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 7

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 8

If you want to add any template (created by macOS Pages or Google Docs) using the combine_pdf gem then you can try with this:
final_pdf = CombinePDF.new
company_template = CombinePDF.load(template_file.pdf).pages[0]
pdf = CombinePDF.load (content_file.pdf)
pdf.pages.each {|page| final_pdf << (company_template << page)}
final_pdf.save "final_document.pdf"