Mixed-reality PDF editor

Client: Leapian

Many 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, 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.