How can I merge all PDF in one file with wickedpdf? - ruby-on-rails

Question

The way I'm working right now is I'm generating multiple pdf files and sending them all one at a time for the user to download, but the problem is sometimes they end up with too many files.
How can I merge all pdfs in a single file before sending them to the user?

Answer 1

I use combine_pdf gem.
To combine PDF files:
pdf = CombinePDF.new
pdf << CombinePDF.load("file1.pdf") # one way to combine, very fast.
pdf << CombinePDF.load("file2.pdf")
pdf.save "combined.pdf"
You can also parse PDF files from memory. Loading from the memory is
especially effective for importing PDF data recieved through the
internet or from a different authoring library such as Prawn:
pdf_data = prawn_pdf_document.render # Import PDF data from Prawn
pdf = CombinePDF.parse(pdf_data)

Answer 2

If you want to use some tool like PDFTk or CombinePDF, all you should need to do is prerender your individual PDFs by using something like:
pdf1 = render_to_string(pdf: 'pdf1', template: 'pdf1')
pdf2 = render_to_string(pdf: 'pdf2', template: 'pdf2')
or
pdf1 = WickedPdf.new.pdf_from_string(some_html_string)
pdf2 = WickedPdf.new.pdf_from_string(another_html_string)
If those tools won't take a PDF as a string, you may need to write them to tempfiles first.
If you don't want to introduce another dependency to merge things, wkhtmltopdf can take multiple pdf files (or urls), and render them all as one pdf with a command similar to this:
wkhtmltopdf tmp/tempfile1.html tmp/tempfile2.html tmp/output.pdf
Knowing this, you could prerender your templates, with layouts and everything, out to HTML strings, then pass them into wkhtmltopdf something like this:
# app/models/concerns/multipage_pdf_renderer.rb
require 'open3'
class MultipagePdfRenderer
def self.combine(documents)
outfile = WickedPdfTempfile.new('multipage_pdf_renderer.pdf')
tempfiles = documents.each_with_index.map do |doc, index|
file = WickedPdfTempfile.new("multipage_pdf_doc_#{index}.html")
file.binmode
file.write(doc)
file.rewind
file
end
filepaths = tempfiles.map{ |tf| tf.path.to_s }
binary = WickedPdf.new.send(:find_wkhtmltopdf_binary_path)
command = [binary, '-q']
filepaths.each { |fp| command << fp }
command << outfile.path.to_s
err = Open3.popen3(*command) do |stdin, stdout, stderr|
stderr.read
end
raise "Problem generating multipage pdf: #{err}" if err.present?
return outfile.read
ensure
tempfiles.each(&:close!)
end
end
And call in your controller something like this:
def fancy_report
respond_to do |format|
format.pdf do
doc1 = render_to_string(template: 'pages/_page1')
doc2 = render_to_string(template: 'pages/_page2')
pdf_file = MultipagePdfRenderer.combine([doc1, doc2])
send_data pdf_file, type: 'application/pdf', disposition: 'inline'
end
end
end
However, this only covers the simplest of cases, you'll have to do the work of rendering the headers and footers if you need them, parsing (or adding) any options you might need.
This solution originally came from https://github.com/mileszs/wicked_pdf/issues/339 so it may be helpful to look there for more details on this strategy.

Answer 3

Try PDFtk. In my opinon, it is the best library for editing PDF files, and there are some gems that wraps it for access from Ruby.