Yes, you can search PDF.
M92 can be used for writing. There are 2 issues. Exactly left-right and top-down lines seem to disapear when exported to pdf. If you leave a pen cca 2 seconds close to a screen without movement, the pen goes to sleep. To make it wake up - the pen has to be placed say 10 cm away from the screen.
It is OK to write ideas, notes, underline text, etc. (No time stress situation) It is not so good to write lots of notes on lecture etc. (Time stress situation.)
So, it depends, what exactly you need. I would recomend M92 for reading and ocasional writing. I personally still use paper for writing, not M92. But I use scribling function of M92 a lot for books and scientific articles. And I use M92 scribling for manuals update when SW has been updated.