You can find something about this in the Adobe Developer FAQ. (It’s a PDF document rather than a web page, which I guess is unsurprising in this particular case.)
The FAQ notes that the use of the command line switches is unsupported.
To open a file it’s:
AcroRd32.exe <filename>
The following switches are available:
/n– Launch a new instance of Reader even if one is already open/s– Don’t show the splash screen/o– Don’t show the open file dialog/h– Open as a minimized window/p <filename>– Open and go straight to the print dialog/t <filename> <printername> <drivername> <portname>– Print the file the specified printer.