PDFs on RoR

To make sense of the earlier post.
The legacy system produces big old A3 job tickets. These exist as PDFs into which the system drops some values - and users write by hand other instructions. It works well so want to replicate it.
My first thought was to use Prawn and Prawnto. Very simple to set up - but building an A3 page in Prawn was a non starter - you have to specify every line, ever text box. Unfortunately you can't open an existing PDF with it.
Plan B was to use an old fave - ImageMagick. It handles PDFs - but unfortunately it rasterizes the image and it looks like crap when you print them out. Not a very good ad for the new system since peopel look at these things every day.
So now looking at iText and using rjb or jRuby to act as the bridge. RJB attracts me as it appears to be simpler.
We will see ...