HOW DO UNDO?

[JLCT]

am working on diagram and want to undo something I put in

[Test Screen Name · Accepted solution]

Very much advise against making a diagram in Acrobat. Painful, error prone and limited. Make it in your normal diagram app and CONVERT to PDF.  If you did that, any changes need to be done in the ORIGINAL app, then you re-make the PDF. So editing a diagram in PDF just doesn't happen.

[JLCT]

AFTER THIS, I WILLLLLLLLLL do as you suggest, but the Control Z did help -
thanks

[Stephanie2452369816uf]

thank you!  control Z is the only answer needed..... thank you!