I am not sure if you can starting an intent with a relative file name. Better use the absolute file name and use am start to view the file:
am start -a android.intent.action.VIEW -d file:///storage/emulated/0/mypdf.pdf -t application/pdf
YES you can switch on USB debugging through ADB provided you bootlaoder is unlocked.
Just have to pull few files ---> edit them ---> Push them back.
It is explained on Github:
The syntax that appears to work as attested over at our sister site stackoverflow is and is explains in detail:
adb shell service call isms 7 i32 0 s16 "com.android.mms.service" s16 "+1234567890" s16 "null" s16 "Hey\ you\ !" s16 "null" s16 "null"
"Isms method number (5 and 7 above) may change with the android version . Read full explanation to understand ...