OK - can we go back a bit?
1. You have four separate Pagemaker files, each set up as 8.5" x 11".
2. You want to combine them into one file. The page size on this file is to be 17" x 11".
3. Two of the original files are to be placed side by side to make the outside of your cover, the other two originals are to make the inside of the cover. We'll call the two pages that will make the outside cover, pages 1 and 4, the inside pages will be 2 and 3.
Assuming all these are correct, do the following:
Create a new document in Pagemaker (File>New). In the dialog box that comes up:
For page size/i], choose tabloid. This should show in the next box as 11" x 17".
For orientation, choose wide. This should reverse the measuremnents to be 17" x 11".
Check both options for double sided and facing pages.
Set the number of pages to 2.
Choose your printer from the Compose to printer box.
Set your margins to be the same as used in your four individual publications, then click OK.
This will create a two page document (although you will see only one page at a time).
Leave this document open, and open up page 4 - the page that will be the back page of the cover when folded.
Group all the elements on the page (select all, then Element>Group) and then copy (Edit>Copy)
Switch back to the new document (it will be listed under the menu item Window) and then paste (Edit>Paste).
Move the group of elements so they are positioned on the left hand side of the first page of the new document.
Repeat all steps for your page 1 - the page that will be on the front of the folded document. This time however, move the pasted group to the right hand side of the first page of the new document.
Rpeat all steps again for your pages 2 and 3 (inside covers), putting page 2 on the left and page 3 on the right of the second page of your new document.
Assuming your printer can duplex (automatic back to back) then just set it to duplex your two page document onto tabloid size paper, and there you have it!
If your printer cannot duplex, then you will have to print one side, turn it over and run it through the printer to print the other side.
Pagemaker is fussy about where the printer's PPD is located in order for duplexing to work. If you are not sure about this, post back.
Also, is the printer a postscript printer? Be aware if you have any EPS graphics in there, they will not print correctly on a non-postscript printer. Convert them to TIFs if this is the case and they will print fine (remember in the Print dialog box to set the TIF printing to 'normal' - which is not the default. It appears in the dropdown list however).
Hope this helps.