Okay, this is NOT intuitive AT ALL. Just trying to add a darn signature to my PDF. And it says I need to "send for signature". When I "send for signature", the W9 that I downloaded from the IRS says that "you cannot edits this file as a form due to its security settings". As I have not touched the file at all when I do this, I should be able to turn off the security settings. But no. I cannot. Any ideas???????
Which Acrobat/Reader version are you using on which platform/OS?
From the description that you provided it looks like you are using Adobe Reader. The form that you are trying to sign is Reader-enabled with certain permissions. It seems that it was Reader-enabled with permissions that do not include what you are trying to do.
It seems to me that you are using a wrong tool. Click on Fill&Sign, then expand "Fill&Sign Tools". Click on "Place Signature". The first time you do that you'll get a dialog which allows you to select signature type and look. The next time you sign it will use the signature you've already created. If you want to change your signature, click on a rectangle to the right of "Place Signature", select "Change Signature", and you'll get the same signature type selection dialog you got the first time you signed.