Yes. AppendPDF Pro will extract page ranges from only one file if you choose. You do not have to append additional pages or files to it for the append to be successful.  Examples below of how parameter file should be constructed.  These examples are setup to extract pages 2, 3 & 4 from Sample4.pdf:

XML Parameter:

<sourcepdfs>
<inputpdf>
<file>c:\Appligent\AppendPro\samples\pdfs\Sample4.pdf</file>
<startpage>2</startpage>
<endpage>4</endpage>
</inputpdf>
</sourcepdfs>

Legacy (text) Parameter

begin_source
c:\Appligent\AppendPro\samples\pdfs\Sample4.pdf,2,4
end_source