Hi,
Thank you for writing to Microsoft Community Forums.
We understand the concern as you are unable to Add notes or Annotate to PDF file in edge that you are editing.
The option you are looking for is currently under development and you will see this in the later updates.
This option is currently available in the Dev Build of Edge and if you are interested in the Insider Channel, you can certainly give this a try. This Dev version of Edge can be used side by side with the normal version of Edge. Please refer this webpage to install Dev Channel: Microsoft Edge Insider Channels
However, we commend and appreciate you for recognizing this in Edge Chromium. You can certainly help us improve the features by sharing your feedback. You can open Microsoft Edge. Click on the Settings & More Ellipsis (…) on the right hand corner and then, select Help & Feedback and select Send Feedback. This is one way where our design team will be able to receive feedback, suggestions and ideas from our customers.
Regards,
Aditya Roy
Microsoft Community – Moderator