Two ways to scan multiple pages into single pdf file
1) Using Scanner alone, No PC connected. From the top control panel on scanner M205b, select SCAN and follow instructions... Stick a USB Thumb Drive, press SCAN, "Another Page" "Yes" "OK" until last page. Then wait for scanner to allow you to pull out the Thumb Drive. You can view the scanned file on your PC
2) Using PC connected to M205b. Buy and load a scanner SW. PAPERPORT recent version is one of the simplest. Install this in your PC/Laptop and follow the instructions. When you have installed the SW and set up the scanner, do not forget to select the option "Scan additional pages". Paperport allows you to set default as .pdf file and also provides many choices.
Hope this helps