Adobe Portable Document file
PDP is a page layout file format used by Adobe Photoshop. PDP files are the same as Portable Document Files (.PDFs) and contain the same information, such as text, images, forms, and other data. The .PDP file extension is not commonly used for PDF files, but is supported by Adobe applications such as Photoshop CS5.
MIME: application/photoshop, image/pdf
Learn more about .PDP files:
Learn about Adobe Photoshop on their website.
Search on IT Knowledge Exchange for .PDP-related questions.