Issue with multiple digital signatures disabling fast web view

Question

Hello, I'm using acrobat 9.1 pro and have some questions regarding an issue using multiple signatures on a pdf.
Why am I asking the question below? My job involves preparing pdf's for submission to FDA. The FDA requires, among other things, that electronically submitted docs have fast web view enabled.
I am currently exploring ways of using digital signatures to sign pdf reports and still make sure they are FDA spec compliant. My issue involves a document that would have multiple signature fields. What I do is create at least two signature fields in the doc and then save and optimize while enabling fast web view. When I sign the first box and save, the file retains the fast web view status. Yet, when I apply and signatures past the first one, the file is subsequently set to fast web view off without any obvious way of turning it back on. I am confused as to why it gets disabled only after the second, and not right after even the first one was signed. And, of course, I would like to know if it is possible to maintain fast web view and how to do it. I'll gladly accept "tinkering under the hood" of the file suggestions if they exist as well.
Please let me know if anything is unclear or you need further information.
Thanks for your time and help.
~Vlad

Answer 1

Hi Vlad,
Michael actual had the correct answer. The purpose of a "Linearized" file (i.e. a file that has been Optimized for Fast Web View) is to get the first page to display as soon as possible so you can start reading without waiting for the rest of the file to download. As an aside, the designated first page doesn't necessarily have to be page 0 (PDF's use a zero based counting system for pages), but usually it is. To quote the PDF specification, "The primary focus of Linearized PDF is optimized viewing of read-only PDF documents. It is intended that the Linearized PDF be generated once and read many times. Incremental update is still permitted, but the resulting PDF is no longer linearized and subsequently is treated as ordinary PDF."
When you sign a PDF file the first time the Save process is a "full save", that is the entire document is rewritten so there are no more than two %%EOF (end-of-file) markers in it. The first EOF designates which page to show first and the second EOF designates the end of the rest of the file (so the browser knows when to stop downloading). However, when you add a second (or subsequent) signature the file is saved as an "incremental save" and all of the new data is tacked onto the the end of the original file. This is so you can do a rollback to the previous signed version and allows Acrobat/Reader to check the integrity of each signature independent of any other signatures. It's the incremental save that breaks the linearized optimization of the file.
Steve