We receive reports that users cannot share from Drawboard PDF to some email software such as Outlook. This is a limitation of the Universal Windows Platform (UWP - Drawboard PDF is a UWP app), and is not an issue isolated to or with Drawboard PDF.
The UWP allows all Windows 10 apps to be developed on the one code platform, and a benefit of doing this is that it enforces a security protocol in regards to sharing to non-UWP apps. UWP apps work in something called an AppContainer or Sandbox, which means that they can only interact and do things within the confines of that environment.
This restricts the ability of malicious codes or bugs to damage important pieces of information that are not within the AppContainer environment. At this stage, Desktop Outlook and O365 Outlook are not within the UWP AppContainer on your computer, and as such Drawboard PDF is restricted in its ability to share to them.
You are still able to share PDFs from Drawboard PDF to the native Windows 10 Mail application, to which you can sync your Outlook account. Follow the following link for setup instructions: https://support.office.com/en-us/article/Set-up-email-in-Mail-for-Windows-10-7ff79e8b-439b-4b47-8ff9-3f9a33166c60