Pentax itself has an extensive repository of manuals for many of their cameras and accessories.
Pentax Imaging - Manuals & Literature
Many of the older manuals are fair/poor quality photocopies that have been converted to PDF files. Newer manuals are higher quality.
The manuals go back to the Pentax H1 (c. 1961).
While the early cameras (and therefore the manuals) were branded under the Honeywell name, the site does not carry manuals for other Honeywell products, such as the Strobonar flashes.
Paul Noble