When copying an image from external location such as MS Word document or a PDF file, then its src points to your hard disk, which is not accessible in Internet.
In order to use images in a web page, they need to be accessible using HTTP protocol - that is, it means they must be uploaded to a web server (which can be your own computer of course, only that the images are provided by the web server software, and not by the operating system).
The automatic image upload cannot be implemented without using ActiveX or some other software, installed on the client, but we do not use either technique because of browser compatibility and that the ActiveX components are forbidden by the corporate networks.
What we suggest is to paste the screenshot in program such as MS Paint and save it. After that manually upload the image using the Upload functionality of the RadEditor's Image Manager dialog and insert it into the content area after that.
the Telerik team
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