Where is the Photoshop File Formats.pdf file?
You need to request the Photoshop File Formats documentation explicitly
On the other hand…
There be dragons!
You could use it to get the most basic elements of a document, as long as you are prepared for hours of trial and error as well, but most features post-5.0 are either described as black boxes, or left out entirely. Clearly nobody inside Adobe uses this document or is properly updating it for third parties.
Update: Form Field Elements
While PSD is an industry standard you may be able to just use Paint.NET to edit them.
Manually converting PSD to HTML.
There is even a book!
Update: Slav has an ActionScript implementation.
See also:
The book of inspiration 