Paste into UR a PDF snaphsot does not work

[Anthony]

I started to have the habit to collect all my info into UR. I came across with the following issue, that probably is more general than the example I describe:
I hava a PDF (let say image only) and I took a snapshot of a part of it: the image is copied to the clipboard. Then I use Win+V to paste the clipboard content (the img) in a new item of UR. But the paste does not work. If I go to UR and I paste the clipboard img to an already present text main pane, the img is ok within the text Item. Yet if I go do Data Explorer and I select an Item (included imported Items) and then I select Edit/Paste or Special Paste, this is not possible since all Paste commands are grey.
Strange thing at last: If I paste the img clipboard to a Word document and I select the img and Ctrl+C, Win+V, everything works again.
Where am I doing wrong?
Thanks
Anthony