Personally, I first split the Full Size PDF into separate pages using an online free tool like
https://www.splitapdf.com/en/
Next I import each of the plans pages into Inkscape (also free)
I know it probably doesn't take long, but is the first step necessary?
When importing into Inkscape it allows you to pick which page of the PDF you want to import.
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But yeah, my process is similar for scoring all the lines on a vinyl cutter.
I tend to import each page into a single Inkscape document so all bulk operations can happen at once (mostly using "edit > select same > stroke colour")
I'll then arrange everything to optimally fit on A1 sheets ...On bigger models this step can often save quite a bit of foam vs the plans as they're laid out on the PDFs.
Vinyl cutter specific, but I'll also extend some of the lines by a couple of mm to enable the cutter head to spin into position on the spoil rather than the work piece.
If I can be bothered, or if I plan to make a few of a design I'll also optimise the path directions & order so it cuts everything with minimal cutter head movements (partially for speed, but mainly to minimize potential for errors). I also arrange the path orders so it cuts each individual part fully before moving on to the next (so any missed steps won't generally matter and in the worst case only a single part will be a write-off rather than the whole operation.
Yeah, it takes a bit of time, but I find the process of editing plans more enjoyable than marking & cutting out parts manually.