Adobe Acrobat 7.x has a new feature that “Enable For Commenting and Analysis In Adobe Reader”, that means you can do comment. in Adobe Reader and save them. but it allows convert one PDF one time, so if you have many PDFs, you need a Batch tools to do it.
I have developed a software that can batch convert all the PDFs of a selected folder(and subfolders), it can save you more time and money, it you like it, you can buy it from https://blog.rubypdf.com/product/
If you have any question, suggestion, please let me know, if you want the source code, also please let me know, thanks in advance.
this is software need .Net Framework 1.1
if you want demo, please email to me.