Alright, I had a lot of fun today trying to figure out how to merge pdf's in our Rails application.

We are using pdfkit to create our pdf's.  What I needed to do was to take several pdf's and merge them into one large pdf.  Frankly I did not think it was even possible.  I found several Ruby gems that were supposed to do the job but everyone I tried was just another PITA dead end.

After getting pointed in the right direction by @m3talsmith, I ended up solving my issue the old school way.  So, if you have done this before with Ruby gems stick with it.  If not, here we go...

[sourcecode language="ruby"]
def merge_pdfs
pdfs = []
pdfs << @bulletin.pdf.path
@bulletin.bulletin_inserts.first.bulletin_insert_items.each do |bii|
if bii.pdf.present?
pdfs << bii.pdf.path
end
end
if pdfs.count > 1
system "gs -dBATCH -dNOPAUSE -q -sDEVICE=pdfwrite -sOutputFile=temp.pdf #{pdfs.join(' ')}"
system "cat '/Users/bob/Projects/bulletin-builder/temp.pdf' > #{@bulletin.pdf.path}"
end
end

[/sourcecode]

I first started with an empty array for pdfs.  Then I went thru a couple of processes to add all the pdfs to the pdfs array.

After that, comes the old school.  Using Ghostscript (gs) we joined all of the pdfs and outputted them to a temp.pdf.  I tried several times unsuccessfully to overwrite the original pdf but I never got it to work correctly.  After creating the temp.pdf we used good old cat command to copy the temp.pdf to the original pdf.

If you know or find a better way, please tell me!!