Recently, I have been unable to open PDF files sent to me via email when using web-based Outlook. I can see PDFs that are saved on my Mac and I can view PDFs within Outlook that are on my non-Mac laptop. I feel the issue was caused with an update or something else on my Mac. I had no issues up until 2-3 weeks ago. I am currently running Sonoma 14.6.1
Make sure you install the latest Sonoma release which is currently 14.7.4 and includes Safari 18.3.
Ensure that Safari is your default browser. Settings > Desktop & Dock > Default browser > Safari
In Finder locate a PDF document and either highlight the file and press CMD + i or right-click and choose Get Info. Ensure Open With is set to Preview app and if Change All button is enabled, click it.
Those are the default settings. You may elect to use another browser as your default such as Chrome or Edge. Both have built-in PDF viewers and might change the default file type association to open your PDF's in the browser instead of Preview app. If you have Adobe Acrobat Reader or Adobe Acrobat DC they may also be set as the default PDF viewer.
Cannot open PDF attachments in Web Based Outlook
