Photo Editor projects may be saved as ACDSee Photo Document (*.APD) files. APD files are automatically associated with the ACDSee standard image decoder, which means that double-clicking on a file with an APD extension will load the 'image' into the ACDSee viewer. If you wish to launch the ACDSee Photo Editor from an APD file, right-click on the file and select ACDSee Photo Editor from the Open With menu.

What are APD files and why would you want to create one?
An option within the ACDSee Photo Editor is to save your work as an ACDSee Photo Document (APD). When you save a project as an APD file, ACDSee Photo Editor saves your work area as well as all of the photos and objects that you copied into the work area. This means that you can continue working with those photos and objects until your project is complete.

If you save your in-progress project to any other file format - such as JPEG, GIF, or BMP - your work area and the photos and objects in that work area will be combined to form a single image object and you will be very hard to make any further changes to the photos and objects in that image.