I don't know that there is one in PDF form. Try the [Time Machine FAQ|http://discussions.apple.com/thread.jspa?threadID=1964018], found at the top of this forum. If you must have a PDF, print that to a PDF file.
There isn't, unfortunately, a Time Machine Manual published by Apple. There are some 3rd-party books about Leopard, that include TM. Check Amazon or the like.
In addition to the FAQ Tip that Thomas provided a link to, you might want to review these:
If you have trouble setting-up or using Time Machine, try the
Time Machine - Troubleshooting *User Tip* at the top of this forum. It will show you how to locate the message(s) that describe the problem, then help you fix it.
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TIme Machine manual????
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