Here are the requirements, the users needs to be able to view uploaded PDFs in the browser. They need to be able to add notes to the PDF and save the updated PDF to the ser
My company, Atalasoft, provides components that let you view document images, including PDFs and annotate them and save the annotations back into the PDF. In our product suite, you would need dotImage document imaging and the PDF Reader add-on. You would be using dotAnnotate through our AJAX web controls. Here is a link to our online demo - the document displayed is a TIFF, but you could use a PDF too.