Hi.

I'm essentially planning to mimic the comment functions on PDF files, but online. That is; a user should be able to log in and upload a PDF file, and then numerous different users should be able to add comments etc to this same file (and view the file, with comments, online).

• External libraries are ok. Free obviously preferred, but commercial ones are fine if they provide a lot of the needed functionality. Note that this is meant to be used in a commercial environment.

• Comments don't necessarily need to be able to be exported from the site. I.e. if the comments are just put as a layer on top of a PDF file (and not in the actual file) that's ok. But obviously the more export functionality the better.

I have looked at a few libraries (using the related questions and google) and while I find some that seem to do sort of what I want I'm not sure they are the bee's knees plus I would like to do as much myself as possible.

The three basic approaches I've thought of is:

• Use some sort of native PDF viewing and then just smack down a layer on top of it where you can move around comments etc.

• Convert PDFs to HTML and work from there. Problem here it would either require proper PDFs (e.g. non-scanned) or really good OCR which seems a bit tedious.

• Convert PDFs to images and work from there. I'm afraid this will create massive images however. We're talking PDFs that can be hundreds of pages. One option would of course to just display one PDF page (image) at a time.

And last - should I look at Silverlight for this or go with ASP.NET?

Ideas and input concerning this project are much appreciated.