The file extension *.PD is used with a few programs. Each program has different needs for the file which makes identifying the source program a necessary part of figuring out which kind of data it holds.
The *.PD extension was used to store a plotter or cutter document, usually used to make posters or oversized printouts, by the program Flex Sign 5 from Beacon Graphic Systems.
*.PD files are also used to store data from MRI machines in the medical field.
Paradox tables hold information relevant to relational database management. Some programs store this data in *.PD files
In the pearl computing language, *.PD files are used to store processor information to make these programs run more efficiently.
No longer in use, Pipe Dream was a word processing and spreadsheet program that stored its data in *.PD files.
Pure Data Patch
*.PD files are utilized as pure data patch files in conjunction with images sounds and custom text.
- Photo Credit Image by Flickr.com, courtesy of Rick Audet