internal - hidden from user - so you cannot get in there and change anything 
sd card - uses internal physical memory (as above) but you have access to the files. It means you can connect to your PC or USB drive and transfer files directly in to there, or copy some to a USB drive for someone using a file manager. However you are doing this outside MS so it could potentially get confused if you start playing around with the structure of the folders, file names etc.
Removable storage is external SD card.
(see the manual, at time of writing, page 14)
Yes you can have large numbers of PDFs and they do not take up much room. If you are scanning probably about 150 to 200 dpi is sufficient (run some tests, especially as you have a 13 inch) and music vector PDFs are very small.
ref: http://zubersoft.com/mobilesheets/forum/...hp?tid=179
sd card - uses internal physical memory (as above) but you have access to the files. It means you can connect to your PC or USB drive and transfer files directly in to there, or copy some to a USB drive for someone using a file manager. However you are doing this outside MS so it could potentially get confused if you start playing around with the structure of the folders, file names etc.
Removable storage is external SD card.
(see the manual, at time of writing, page 14)
Yes you can have large numbers of PDFs and they do not take up much room. If you are scanning probably about 150 to 200 dpi is sufficient (run some tests, especially as you have a 13 inch) and music vector PDFs are very small.
ref: http://zubersoft.com/mobilesheets/forum/...hp?tid=179