Can we take a moment to remark on how wonderfully useful PdfJam is? Behind the scenes it’s just LaTeX. Thus you might be surprised to notice that
pdfnup --nup 1x1 --paper a5paper --no-landscape image.png
Is an excellent way to turn an image—say, a bunch of screenshots of a page which you concatenated with
convert image1.png image2.png image3.png -append image.png
Into (say) an a5 pdf, ready to be turned into a full-length pdf with
pdftk *.pdf cat output out.pdf
And then laid up into a booklet with
pdfbook2 out.pdf
I’ve used pdfbook2 over pdfbook as it adds margins—which normally I don’t want, but here it is useful as the nup-d pages probably don’t have very large margins. Of course there are various ways of customising it. An even better way of converting pngs of a text document (say, a scan—though beware copyright: you’re probably alright for personal use but IANAL) into pdfs is
tesseract image.png image-ocr -l fra+lat+grc pdf
With languages set accordingly, initially in order of provenance. This produces a pdf with ‘invisble’ ocr-d text you can select and copy-paste, and it’s really good. But Tesseract and Scantailor (an excellent program for extracting, sharpening, monotoning and generally adjusting scans) are for another post and another day.