Add margin to PDF file when merging using PDFTK or similar

Question

I have a large collection of half-page sized PDF cut-sheets that are held in a folder on my Linux server. A user to the site will want to create a booklet from a subset<

Answer 1

Even if it is a bit late, but it might help someone. In response to @ElkeSpaak comment, it's the package texlive-extra-utils:

dpkg-query -S /usr/bin/pdfcrop 
texlive-extra-utils: /usr/bin/pdfcrop