The PDF documents here are the scanned manual pages to 1st Edition Unix,
taken from Dennis Ritchie's web page:
http://cm.bell-labs.com/cm/cs/who/dmr/1stEdman.html

A copy of the above HTML file is also cached here, but most of the
hyperlinked documents are missing.

UNIX_ProgrammersManual_Nov71.pdf is a file from bitsavers:
http://www.bitsavers.org/pdf/bellLabs/unix/UNIX_ProgrammersManual_Nov71.pdf
It appears to be an aggregate of most of the PDF documents noted above.