Some in sharpies, some in blue pen, some in black pen, use different color pens to cross things out, as mentioned earlier.
My floppies got ruined in a basement flood a few years back so I can't give you actual vintage ideas, so I have to go from memory.
The three that I definitely remember having from that era are:
DOS 6.22 Kip's games Backups
Put the "Backups" floppy in your backpack/purse, carry it around with you for a week or two, get a patina on it.
On Tue, Oct 1, 2019 at 3:06 PM Charlie email@example.com wrote:
Heavy on the dates!
In pen #1, crossed out with pen #2: Shareware summer ’92 In pen #2, crossed out with pen #3: English 141 homework (spring 93) Added in pen #1, also crossed out with pen #3: + term paper 5/93 In pen #3, crossed out with pen #4: System files BACKUP, 7/93 Added in pen #3, crossed out with pen #3 and #4: , 7/20/93 Added in pen #3, crossed out with pen #4: , 8/93 In pen #1, crossed out with pen #1: Games from Kim In pen #1, circled, in attempted wildstyle, heavily crossed out with pen #2: GAMES FOR KIM, FROM PAT, PLEASE RETURN In pen #2: Math 390, fall 1995 Added in pen #1: + coursework backup
Then all crossed out with an almost-dry red Bic with a big X and the label CORRUPTED? getting squeezed toward the edge of the paper.
And building on what sincarne said, for maximum palimpsest authenticity, print out some fake commercial labels (BusinessPro for Professionals 2.4, Carnauba Ltd, (602) 555-1888, 230099 Birefringent Pkwy, Trimaran AZ 85058, Installation Disk 1 of 3, do not duplicate) on disks of brand-ish colors, then cross out or blank-address-sticker over them to make the user’s writing surface.
The one thing that would make this look like a fakey prop to me would be one neat label per disk in the same pen and handwriting: unless, of course, it’s made clear in-story that the person who owned the disks was profoundly troubled.