Answered
I have a PDF file whose page size (under File/Properties) is "9.03 x 6.94 in". When I view it in Acrobat 8.0 Standard as "Actual Size" it measures as 8.5 x 11 inches. By this I mean I am putting a ruler on my monitor and measuring the page and those are the dimensions on the screen. It seems to me AcroBat has decided to show "letter size" not actual size.
This is important to me because I am creating the file myself (FYI with LibHuru library not JavaScript) and I am trying to make sure the sizes of things (images) are what I expect. My calculations with a user unit of 1/72 inch do not work out of course because everything is stretched. Is there an "Actual Actual Size" option?
If you have a 22" monitor standard 4:3 format the physical size width x height is 17,6"x13,2". Running at a pixel resolution of 1600x1200 this will give you an effective resolution of: 90.91 ppi
On a Mac this is higher than the native res of 72 ppi so to view the file in real size you have to set the zoom value to 126,26 %
Om Windows the 90.91 ppi effective resolution is less than the native res. so in order to vie the page in real size the zoom value should be at: 94,70%
To make this all the more annoying the zoom values vary from monitor to monitor based on the actual size of the monitor, the active screen area, the native resolution of the operating system, and finally the pixel resolution set in the OS.
All in all, you can not use a ruler to meassure things on you monitor. Only the size defined in the document matters, if the document is 9.03x6.94" then that is the size it will print in. No matter what you see on the screen.