I used to use hidden text to beat the resume keyword scanners, but it didn't help much.
Steg?
People used to do that all the time back in the hotjobs/monster/dice days (around 08' 09') They would add an extra page on their resume and put every buzzword you can imagine in white text. All it did was make them seem desperate.
What do you hide?
The stuff that I didn't do, but helps beat the ats systems. To be fair, it didn't help.