When you double click on a PDF attachment in Outlook, you are being asked whether you would like to open or save the file. You want to skip this question but the option “Always ask before opening this type of file” is grayed out.
To enable this option, you must explicitly run Outlook as an administrator even when logged on as administrator, since this action cannot be performed with standard user privileges.
To run Outlook as administrator, complete the following.
1. Exit Outlook.
2. Hold CTRL+SHIFT while clicking on the Outlook icon to start Outlook with administrator privileges.
3. Click on Yes to accept the User Account Control (UAC) security prompt.
4. Open the attachment and untick the checkbox “Always ask before opening this type of file”.
5. Close Outlook and start it normally.