I have a small program that was written to allow a person to find and view drawing files (PDF) on a Tablet pc. I would like to add the ability to mark up the drawing and save the changes. Is there anything out there that might make this possible? I have found a program called 'MetaDraw3' that I think I can make work but it would require me to convert the PDF to an image file and then back to a pdf after making changes. I would like to avoid converting if possible. Any help or advice would be greatly appreciated.

Thanks in advance.