Hi @Damien Peden - Linkup Paints ,
Welcome to our forum!
Does this issue occur with other attachments, such as .doc?
We used to have this issue periodically saving from Chrome but we were able to add a registry edit to stop that
According to your description, i notice that the issue also occurs with the PDF files saved from Chrome, so i'm afraid that it's not related to Outlook desktop client. In order to confirm this, it's suggested that you could try to configure your account in other email client, such as Mail, and then save the PDF files to check if you can easily open the saved PDF files.
If the issue persists, considering the impact of your current computer, please do the same test in other computer to check if there're any differences.
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