Watermark in existing PDF in Ruby

Question

I would like to add a dynamically generated text. Is there a way to watermark an existing PDF in Ruby?

Ez

Answer 1

This will do it:

PDF::Reader to count the number of pages in the file.

Prawn to create a new PDF document using each page of the input pdf as a template.

require 'prawn'
require 'pdf-reader'

input_filename = 'input.pdf'
output_filename = 'output.pdf'

page_count = PDF::Reader.new(input_filename).page_count

Prawn::Document.generate(output_filename, :skip_page_creation => true) do |pdf|

  page_count.times do |num|
    pdf.start_new_page(:template => input_filename, :template_page => num+1)
    pdf.text('WATERMARK')
  end

end

However, in my testing the output file size was huge with the latest Gem version of Prawn (0.12), but after pointing my Gemfile at the master branch on github, all worked fine.

Lerner

You can pass the :template option to Prawn::Document and then just iterate through the pages that way. That will keep the output file size much closer to the input file size. – Styria

Prawn no longer supports editing/combining two PDFs into one. Check the answer by @Myst for an up-to-date solution. – Kettie

Answer 2

Another option is to use PDFTK. It can be used to add a watermark and create a new PDF. Maybe prawn will do the same thing with it's templating.

pdftk in.pdf background arecibo.pdf output wmark1.pdf

Some more info: http://rhodesmill.org/brandon/2009/pdf-watermark-margins/

There is a ruby wrapper gem called active_pdftk which supports backgrounding, so you don't have to do the shell commands yourself.

Xanthous

Answer 3

Prawn doesn't support templates anymore...

Try the combine_pdf gem.

You can combine, watermark, page-number and add simple text to existing PDF files (including the creation of a simple table of contents without PDF links).

It's a very simple and basic PDF library, written in pure Ruby with no dependencies.

This example can fit your situation (it's from the readme file):

# load the logo as a pdf page
company_logo = CombinePDF.load("company_logo.pdf").pages[0]

# load the content file
pdf = CombinePDF.load "content_file.pdf"

# inject the logo to each page in the content
pdf.pages.each {|page| page << company_logo}

# save to a new file, with the logo.
pdf.save "content_with_logo.pdf"

Muss

Content file text not visibing, i've noticed the font color is geting white when creating template using mac pages – Inexpugnable

@Inexpugnable , this might be an issue (or your PDF's background might be an opaque white rather than transparent), but this is definitely not the gem's normal behavior. – Muss

Answer 4

Check out Prawn(http://github.com/sandal/prawn) for just ruby and Prawnto(http://github.com/thorny-sun/prawnto) for Ruby on Rails.

You are probably going to want to either use the image embedding functionality or the background image functionality.

Here's an example of using a background image http://cracklabs.com/prawnto/code/prawn_demos/source/general/background

Shelter

Prawn is only able to embed images to a fresh pdf created with prawn not an existing one ... so it doesn't work for me. – Ez

ah, missed the existing part in your post. Sorry about that. I don't believe there is, unless you were to convert it to an image and then watermark it. – Shelter

Actually, it seems that Prawn can edit an existing PDF if you use that PDF as a template: groups.google.com/group/prawn-ruby/browse_thread/thread/… & github.com/yob/prawn/tree/templates_2010 . I have not personally used these, but the information seems somewhat recent? – Fiord

Answer 5

Use Ruport.

1st result for Googling ruby pdf watermark.

Knox

Duh... just shows the limits of Google. I'm looking for the same thing, and Ruport is not it. – Encomiastic

Ruport uses PDF::Writer. PDF::Writer only creates PDFs. No go. – Falgoust