To open a PDF at page 100 the follow works
<path to Adobe Reader> /A "page=100" "<Path To PDF file>"
If you require more than one argument separate them with &
I use the following in a batch file to open the book I'm reading to the page I was up to.
C:\Program Files\Adobe\Reader 10.0\Reader\AcroRd32.exe /A "page=149&pagemode=none" "D:\books\MCTS(70-562) ASP.Net 3.5 Development.pdf"
The best list of command line args for Adobe Reader I have found is here.
http://partners.adobe.com/public/developer/en/acrobat/PDFOpenParameters.pdf
It's for version 7 but all the arguments I tried worked.
As for closing the file, I think you will need to use the SDK, or if you are opening the file from code you could close the file from code once you have finished with it.