PDF tool comparisons
Every other comparison of PDF tools compares feature lists. These compare the things that actually decide it, and that only this index holds: whether your files leave your device, whether the redaction genuinely removes content or only draws over it, and what each one costs to start, with the period that figure covers, rather than the annual rate the vendor advertises.
iLovePDF vs Smallpdf
The two biggest browser PDF toolkits, both of which upload your files.
SnackPDF vs SimplePDF
Two browser tools whose editing says the file stays on your device.
PAC vs axesCheck
The same PDF accessibility checker, twice, from the same company.
Same owner - not independent options
Adobe Acrobat vs Foxit PDF Editor
The two best-known paid PDF editors.
iText vs Apryse
Two developer PDF libraries, and one company owns both.
Same owner - not independent options
DocuSign vs Dropbox Sign
The two best-known e-signature services.
veraPDF vs PAC
Two ways to check a PDF against PDF/UA.
Tesseract OCR vs OCRmyPDF
The OCR engine, and the tool built on top of it.
iLovePDF vs PDF24
A paid browser toolkit against a free one, on the fact that matters most.
Smallpdf vs Sejda
Two browser toolkits that both upload your file, at very different prices.
This is a deliberately short list rather than every possible pairing. There are 155 tools in the index, which is thousands of combinations, and most of them would tell a reader nothing. Each comparison here is one people actually make, and carries a written judgement about what decides it.