There is no simple answer to your query without knowing whether the PDFs were generated initially as text PDFs (as in, were typed or otherwise fed the text which was formatted) or are image scanned PDFs of text material.
The former are easy to manipulate via any number of methods, the latter are not.
Also, depending on how much text you're trying to "hack out" and whether you are trying to re-integrate the files that have had text trimmed out PDF Split and Merge can come in quite handy.
Brian AKA Bri the Tech Guy (my website address is in my profile) Windows 10 Home, 64-bit, Version 1709, Build 16299
Here is a test to find out whether your mission in life is complete. If you’re alive, it isn’t.
~ Lauren Bacall