Uploaded August 2018 | Updated September 2026, 44 minutes ago

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PDF documents lead a double life, on screen and as hard copies.
But when people modify hard copies (such as the proofreading
marks that copy editors use, or annotations by students on their
lecture notes), the digital versions stay the same. If you have a
photo of an annotated document, it should be possible to match
this against the PDF image, extract the annotations as an image
diff, and apply them to the PDF. The simplest approach is just to
overlay the annotation ink as a bitmap, but ideally, proofreading
marks should be interpreted as edit operations on the original
document, potentially including OCR of any clearly handwritten
text. Your client can provide some specialist assistance in PDF
processing.