Prawn gem: How to create the .pdf from an *existing* file

Hi there,

Can anybody show me (maybe copy/paste a simple code example) how to
create the .pdf file from an existing (.xls) file, using the Prawn gem?

Basically, I’d need the command that takes an existing (.xls) file to
save it as a .pdf, afterwards.

(I’m asking because the Prawn documentation at
http://prawn.majesticseacreature.com/docs/ seems to be gone since quite
a while - it’s not even usable via Google cache, anymore…)

Thanks a lot for any help with this!
Tom

Turns out the Prawn gem cannot handle existing files…