Opening PDFs automatically with Firefox and, without any changes I might make, saving them with the download function in Firefox, actually ruins the functionality and data entry function of that file. Specifically this happens with PDF files downloaded from the (not all that amusing) PDFs from the FINCEN, (US Financial Crimes Enforcement Network). I do not see why and how Firefox thinks it is allowed to change files that are simply downloaded and saved on Firefox. In other words, it seems that Firefox strips away certain "permissions" and/or "functions" (like built-in lookup, menu or choice boxes). This means that the file so downloaded via Firefox can no longer be used to properly fill in data, or to look up and choose data items within the file. (I see many times that ANYTHING having to do with "permissions" tends to be an intractable and unsolvable problem for software makers & experts, so, if you do not know right away how to solve the problem, it will probably take you several years to figure this out.) The PDF in question is created by a government agency. If you have ever dealt with a government agency, then you know that they act sort of like Adobe or Microsoft: "They don't respond, or they do respond & say they do not understand, and if they understand, they are either unwilling or unable to fix the problem." If there is a switch or option within Firefox, which lets me tell Firefox "Save this file exactly like it is received, nothing added or removed!", that would be nice. I just have not found such an option yet, and it would be nice if it might get provided someday. I will share my browser data, but I am sort of convinced that a detailed question like mine will not be addressed within that shared data.