Hi Federicof,
Sorry for the delay in response.
We have received few reports related to this issue and sadly we have not been able to reproduce the issue in-house.
- Please check if you have any pending updates for Reader.
- Check if the issue is reproducible with all the files you are trying to highlight.
- Is there any other tool under comments/annotation that is causing this issue? Or it just the highlight tool?
- Have you tried reinstalling the application?
- If not, try uninstalling and try reset preferences How to reset Acrobat Preference settings to default. Restart the machine and try again.
Please let us know if that helps. Or if you have already found a resolution/workaround to this query, please reply to third with your findings that will help.
-Tariq Dar