Can I import my last two years tax returns if they're in pdf format

Import to where/what?   You can only Transfer a 2023 tax data file ending in .tax2023 into 2024.   You can transfer a 2023 pdf file but it is limited.   A pdf only transfers basic info like your name, address, ssn and AGI.   Might as well enter everything for 2024 from scratch manually.  

into turbotax so it can use the info for this year taxes as a baseline

Not really.   Did you read the rest of my post?   Any more questions?