What are suggested methods for saving a screen shot of documents (church register etc)

I am trying to figure out the best way to handle getting views of the actual documents. Many of the actual documents will open as a pdf document. When I save it as media, it saves the link to the internet source.

Is there a better way to handle this? I'd love to be able to use the 'screen shot' of the parish birth register, for example, as the lead picture on the family tree format, in lieu of actual person photos.

How can you save it as a jpeg?

thanks, all!