I have several A4 PDF documents which I would like (two into one) \"glue\" together into A3 format PDF document. So I will get from 2PDFs A4 a single one si
On the Postscript side, a tool named pstops is able to rearrange pages of a Postscript file in any way you could imagine. I've not heard of such a tool for PDF. But pdf2ps and ps2pdf exist. So a not-so-ideal solution may be a combination of pdf2ps, pstops and ps2pdf.
What you want to do is imposition. There are commercial tools to impose PDFs such as ARTS crackerjack and Quite imposing but they are pretty expensive (US$500), require a copy of acrobat professional and are overkill for imposing 2 A4 pages to an A3 sheet.
I just came across a nice tool on superuser.com called PDFjam that can do all of the above in a single command:
pdfjam --nup 2x1 file1.pdf file2.pdf --outfile DONESKI.pdf
It has other standard features like page size plus a nice syntax for more sophisticated collations of pages (the tricky page re-ordering necessary for true booklet-style page imposition).
It's built on top of TeX which is, whatever it is. Installing is a breeze on Ubuntu: you can just apt-get install pdfjam
. On Mac OS, I recommend getting BasicTeX (google "mactex basictex"; SO thinks I'm a spammer and won't let me post the link).
This is a lot easier and more maintanable than installing both pdftk and Multivalent (on both Mac OS for dev and Ubuntu for deploy), which wasn't going so well for me anyway...!
You can put multiple input pages on one output page using BookletImposer.
And you can change page orders and combine multiple pdf files using PDF Mod.
With these two tools, you can do almost everything you want with pdf files (except editing their content).
I would combine the two A4 pages into one 2-page PDF using pdftk. Then Print to PDF using something like PrimoPDF, and tell it to print to A3 format, two pages per side.
I just tested this printing some slides from PowerPoint. It worked great. I selected A3 as my paper size in PowerPoint, and then chose to print 2 pages per side. Printed to Primo and voila, I have two A4 slides per A3.