Have you ever received a PDF file, only to discover once you open it the pages are upside down?
This happens to me quite frequently at work, when multiple pages are scanned to PDF using a sheet feeder. If the paper is not in good condition, due to stapling or whatever, the scan is done from bottom to top and unless the full Adobe Acrobat is used can not be rotated before sending.
While this is aggravating, if you want to read the document directly from the computer, there is a way to do this without turning you monitor upside down or standing on your head.
The following directions apply to Adobe Reader v7.0.8, but should be similar, if not the same, in earlier versions:
If you are going to print out the file to read it, rotating is not necessary.