I believe that you are using the Project->Publish option which is a bit different.
I use the publish command from the manu (File->Publish) and plot to a pdf printer (like Bullzip PDF for instance). This merges all the drawings into one pdf. You need to create a page setup in the first drawing of the list which will use the "pdf printer" and apply this to all the drawings. This method doesn't add any "-Model" text to the filename. In fact you enter the name of the pdf. Under the Publish Options you van choose if you want a "Multi-Sheet File" or a "Single-Sheet File" controlling in this way if you want them merged or separated files.
