The very appearance of you machine would indicate to me that the only way for you to scan multiple pages is to load and scan them one by one, as there is no automatic document feeder on the machine, just a manually lifted cover for the platen (glass).
However you can get a manual here:-
HP PSC 700 User Manual
by clicking on the green "Download" button near the top of the page, and following the subsequent instructions to download the pdf file to your computer for future reference.
HP provide a number of support options as well, which can be accessed from this page:-
HP PSC 750 All in One Printer support
Hope this is helpful, if so would you please register that with Fixya