During scanning documents it gives an error : "Unable to capture image. An unknown error occurred (-16800)" and sometimes just closes the app itself, making me scan the bunch of pages all over again.
While commenting if I was using the continuous reading mode then I am able to scroll but if single page mode was used before commenting the document can't be scrolled to next page with two finger, that makes adding handwritten notes on consecutive pages a bit hectic process.
You posted this to the Adobe Reader forum. Acrobat Pro lets create a PDF from Scanner. Reader does not. What are you actually using?
There is an Acrobat forum for scanning and a different one for commenting, and many other forums for other specific Acrobat issues. This post can be moved to one of those two forums if you actually have Acrobat, and not Reader.