You have multiple options for copying to the computer. You can
a) Use the companion and perform the Library backup from there (File->Library Backup)
or
b) Copy all of the files from /sdcard/Android/com.zubersoft.mobilesheets/files/ and also go inside MobileSheets->Options->Advanced->Export Database, select a location for the mobilesheets.db file, and then copy that file to your computer as well (the db contains all your song data, annotations, setlists, etc). If you use this method, when it's time to restore your library, you will have to copy the mobilesheets.db back to a temporary location (pick anywhere on the sd card), then go to MobileSheets->Options->Advanced->Import Database, and select the file you exported. An alternative to this is to store the database in the same folder listed above which requires checking the top option on the Options->Advanced screen (store the database on the sd card).
a) Use the companion and perform the Library backup from there (File->Library Backup)
or
b) Copy all of the files from /sdcard/Android/com.zubersoft.mobilesheets/files/ and also go inside MobileSheets->Options->Advanced->Export Database, select a location for the mobilesheets.db file, and then copy that file to your computer as well (the db contains all your song data, annotations, setlists, etc). If you use this method, when it's time to restore your library, you will have to copy the mobilesheets.db back to a temporary location (pick anywhere on the sd card), then go to MobileSheets->Options->Advanced->Import Database, and select the file you exported. An alternative to this is to store the database in the same folder listed above which requires checking the top option on the Options->Advanced screen (store the database on the sd card).