In the past, did we talk about the Skim PDF viewer, and its command-line component that can merge PDF, or extract ranges of PDF pages into an output PDF? This tool is inside the Skim application, and to use it on the command-line, one makes a UNIX soft link from the application into a folder location in their default (/usr/local/bin) search path. It may, or may not be as robust as cPDF.
skimpdf embed IN_PDF_FILE [OUT_PDF_FILE]
skimpdf unembed IN_PDF_FILE [OUT_PDF_FILE]
skimpdf merge IN_PDF_FILE_1 IN_PDF_FILE_2 [OUT_PDF_FILE]
skimpdf extract IN_PDF_FILE [OUT_PDF_FILE] [-range START [LENGTH] | -page PAGE1... | -odd | -even]
skimpdf help [VERB]
SkimPDF command-line client, version 1.1.6