How to combine (partially scanned handwritten) comments from multiple sources into the original pdf?

Question

When asking colleagues for feedback on a PDF, some of them prefer adding hand-written comments on its printout instead of using the pdf comment functions of acrobat/reader, and send me the scan afterwards. That's ok to read, but troublesome if you want to merge multiple comment sources into a single document. I'm fine with having the handwriting, i.e. no OCR (or manually recreating it as PDF comments) is needed, but I'd like to have only the additions to the original pdf superimposed as layers (one per commenter) onto the original PDF, so its original features such as full text search will still work. If only one commenter exists, I can import the original PDF as background layer (which apparently can only be done page by page), but if

• some feedback is PDF comments
• other feedback is scanned handwriting
• in total, there are at least 3 different documents, so some merging is required

how can I merge all that into a single useful document?

Answer 1

Use layers in the pdf. When exporting pdf tick the "Create adobe Layers".
Then when you have it open in Acrobat use Layers menu to add the pdf's with hand annotations as next layer.
I don't think there is a limit to the amount of layers.

Answer 2

I would recommend opening all of them in Photoshop on seperate layers. Select and mask the desired comments, and move up/down in the layers as needed, until they're on top of the original document and positioned correctly.