Is there a tool to simply join 2 pdf pages in one? It seems a hard to find an answer to such a simple request:
I have a pdf file with 16 pages A4 size. I would like to make a 'spreads' view of it, this means that page 1 and page 16 (cover and backcover) should remain A4 size while all the pages in between should become A3 size.

I tried the following:


Using Preview.app I can display the pdf the way I want but I can't
save it for use with any other pdf viewer.
Print to pdf the in between pages with the "multiple pages per sheet" option doesn't
work for me because page margins are inserted in between the a4
pages.


I know some a good pdf editor can do this but these tools are expensive and I don't need it for anything else. With Windows I used a simple freeware tool.

Do you know how to do it for Mac?
You can try PDFSam.  PDFSam stands for PDF Split and Merge. Its a free open source app. There is a Pro version you can buy but the basic version is free.