Show HN: Pdfscale
github.com
Bash Script to scale and/or resize PDFs from the command line.
Uses ghostscript (gs) to create a scaled and/or resized version of the pdf input.
github.com
Granted, this is something I already have a workflow for, so I don't actually need this particular tool. But if I were assembling such a workflow, I might well consider this as part of it.
Depending on the site and what you are doing it may auto-rescale, I try to make it exact though just to prevent any nonsense on their end (and in Adobe PDF you can print tile to check it out as well in actual size).
Alternatively, generate poster (~ 1 meter x ~1 meter ) by printing/taping together regular size paper sheets.