First, any file you locate in Finder can be deleted. If you don't see "Move to Trash", just drag the file to the Trash icon on your Dock.
You don't have to "transfer" pdfs between Adobe Reader and the Preview app. You open the pdf with either app, whichever you choose. You can right-click (or Control-click) any file and choose "Open with" to choose which app you want to use to open the file.
Ok I will go on, if this is not a hassle!
The pdf's are sent to me via a yahoo email address ( I know nothing about this, except yahoo.com )
I try clicking on the enclosed ( in the email ) PDF file both using just control click, and control click plus option key, but regardless, Adobe takes over- I have yet to ( I have seen these at other times ! ) se the sub menu "Open with" this or that application; instead I get the default Adobe deal.
What am I doing wrongly?