PDD is a layered format used for image files created with Adobe PhotoDeluxe. This format uses a similar file structure as the PSD format (the native file format for Photoshop files). Adobe PhotoDeluxe was replaced by Adobe Photoshop Elements in 2002. Since then, PDD is used as a secondary format for Photoshop files. This format stores all the layer data you create while working with the image in PDD file. The image data is stored in 8 bits per channel, 16 bits per channel, and 32 bits per channel in a PDD file.