I'm developing Online Signature System.
But, i don't know what is good solution.
Our requirement and process are as follow.
1. User(A) can upload his document (MS Word or PDF or Image) online. document is not one page. document can be composed of a few pages.
2. User(A) can modify uploaded document a little online and save it (i'm not sure file format)
3. User(B) can view/fill something in blank of User(A)'s modified document online. But User(B) can't modify User(A)'s modified document. User(B) can just fill something in blanks.
4. And User(B) can write his signature(s) in a few place of that document. and save it.
5. When User(A) see that document online, User(A) can see that document that User(B) fill blanks and sign.
PHP is not required. We don't know PHP.
All system and process run on all browser and support HTML5.
Also, you can provide File upload part supported in all browser.
also, User(A) can print ^^)