A:
1) Yes. PDF, JPEG, OCR ( editable text), and everyday scan.
2) I think that would depend on what type of file you are saving it as. I've scanned things and saved them as PDF and they were not overly large. You can use the black sizing bars to "size" the document so that there is no white space and then under "Crop" choose "Selection" from the drop down list (the default is original).
3). I have yet to scan multiple pages since I've only had the printer for a few weeks. However, since you have the option of scanning either from the flatbed or from the automatic document feeder, I would imagine if the documents were scanned by the automatic document feeder, that it would be able to scan several pages just as it faxes several pages via the automatic document feeder.
Hope this helps :-)