Mohammed Abdul Waheed 

Somehow you registered Office files in such way. Please go to your Windows settings, chose Apps, then go to Standard Apps, chose the corresponding Office app (here: Word) and make the corresponding setting. Or type docx in the search field and chose the app to open it (again: Word). You can also run a repair installation of your Office.

Mohammed Abdul Waheed 

Any chance they have more than one file ending? Like example.docx.sdlxliff ? Explorer (and other programs) sometimes try to be user-friendly and do not show the proper file ending. This is often used for hacking, when people send a file like readme.docx.exe or so, and douple-clicking it will run the executable. In this case it does not look malicious, but might be worth saving the files to hard drive and look at their "Properties", which should show you their real, full file name and ending. Otherwise Jerzy is right and your Windows settings are messed up.

Daniel

Thanks Jerzy. I will try that for sure.

Thanks Daniel. No, it's not the case here. These are files received through a secure office network my colleagues and I use, so I will try the Windows settings and hopefully that will resolve the issue

Mohammed Abdul Waheed 

Before you do so, think about what Daniel Hug  said. Unfortunately I did not think about the obvious...

So please first check, if you are showing file name extensions in Windows (default setting is NOT to show file name extensions): https://www.gadgetsnow.com/how-to/how-to-see-file-extensions-in-windows-11/articleshow/92177709.cms or similar articles, found via Google.

It was indeed a Windows settings issue. I had a look at the article you sent and did some searching online. While I could not find an exact precedent to mine, there was a user on a Microsoft forum that said Outlook was changing all their Word files to PDF and there was a solution provided by Microsoft. I tried it and it was successful. It is simply to close Outlook, search for "Default Apps" in the toolbar at the bottom of the screen and click "Rest".

Thank you for your help and you time!

Mohammed Abdul Waheed said:

"Rest"

I hope you don't mind me correcting... click "Reset"

( for any future readers )