First, I wouldn't use any of PDF creators/distillers to "print" a document from Scribus to PDF. Scribus excels in PDF creation so use its own way: File > Export > Save as PDF (or simply click PDF icon on the toolbar).
Now, for imposition tools. If bookbinder doesn't work for you (though it should; check your home dir for a new folder named after the PDF you're imposing), try multivalent, it's very nice little app, despite the fact that you'll be using commands via Terminal/Command Prompt. If you're ready to give it a try, download the file from
here (this is an older version which includes all necessary tools, unlike the last version). Here's an example command (on Linux, Multivalent.jar and PDF docs in the same folder; for Windows check
here):
java -cp Multivalent.jar tool.pdf.Impose -dim 2x1 -verbose -paper-size "11x8.5in" -layout "2,3,4,1" Test.pdf
An example file with Scribus file, bookbinder and multivalent outputs can be downloaded from
here.