I am blogger and product reviewer. As such I deal with a lot of prototype products, and "insider" information. There are times when I am asked to sign a Nondisclosure Form or something similar and I wanted to know if there was a way to supersede that with my own form or statement within my work profile to state something to the point of "should I find fault or other hazards or ethical issues with the product, my integrity and rights as a reviewer/blogger/etc hereby revoke any previously signed documents in order to maintain personal integrity and liability" Or is the document signed between me and said company/persons legally binding regardless of my Independent Contractor clauses?
Let's say I have some information and I tell you "You can get this information but only if you sign my NDA". It's your choice what you do. You can offer to sign a different agreement, or refuse to sign the NDA. Then I have the choice not to give you the information you wanted.
Usually companies offering information for NDA had a lawyer checking their NDA, which costs money, and they might sent that same NDA to 100 bloggers. If they accepted your NDA instead, they'd have to check that through a lawyer. One lawyer for one blogger instead of one lawyer for hundred bloggers. That's quite costly, so the answer will be "no".