Combine PDFs using Preview in Mountain Lion (other threads read)

Question

I have reviewed several threads about combining PDFs in Mountain Lion.  I will ultimately learn Automator but for now, I have a relatively simple question:
1) I open multiple PDFs in Preview, one window per PDF
2) I drag thumbnail pages from documents 2 through n onto document 1 so that it makes one long document.  ie. one unbroken string of pages and not sections within a PDF
Question:  How do I save this combined document without deleting or affecting the first document?
Duplicate causes one of the uncombined documents to pop up with the filename highlighted.  I don't see how to give the combined document a new filename for saning
Rename gives me a file of the three combined documents but the first document disappears
Save overwrites the first document with the combined document
I must be missing something simple.  I recognize that the lack of "Save As" is a sensitive issue but ultimately, that's what I want to do:  Save the combined document with its own filename and have the individual documents intact.

Answer 1

ncasey88 and Old Toad:
Thank you for your quick responses.  Unfortunately, with both methods, the first PDF gets updated.
e.g. Files are 1.pdf, 2.pdf, 3.pdf, each is one page long, and I open each in its own Preview window.  I drop thumbnails of 2.pdf and 3.pdf onto the thumbnail area of 1.pdf.  I export or print into a file called 123.pdf 
Result:  1.pdf and 123.pdf have the same information (all three files).  2.pdf and 3.pdf are unchanged but 1.pdf is three pages long.