Hi Romina,
If you have installed anti-virus software, please add Word to exclusion list and check if the issue occurs.
If it is not caused by anti-virus software, please first restart your Mac, try saving documents in Desktop, moving the old documents to Desktop and check if the issue occurs. If the issue doesn't persist, please make sure the folder where the documents are saved have Read & Write permission (Right click on the folder > click Get Info > Sharing & Permissions, you may unlock the Keychain to change it).
Besides, if the issue persists, please provide the following information:
- Are documents saved in local or network location?
- If you create a new document and save it, does the issue occur?
- What are the common features of the affected documents (file format, location and so on)?
- What actions have you performed before the issue occurred for the first time? For example, a software installation and a system update.
- Your Mac OS version (e.g. 10.12.4) and Word version. For Mac OS version, from the Apple menu, choose About This Mac. The version number appears beneath “macOS” or “OS X.” For your Word version, choose Word in the top menu bar > About Word and please capture a screenshot of the window.
Thanks,
Tina