A portable document format is more commonly known as a “PDF.” You’ve undoubtedly experienced a lot of these in your past. You will often experience these when working with fillable forms or official documents that need to be signed. These can be saved out Photoshop, Illustrator, InDesign, or even print to PDF in your web browser.
If you want to get really fancy with PDFs, you can password protect them, meaning you have to key in the right password in order to open it. What this is really useful for is creating a nice protective bubble around your file. PDFs are excellent to use whenever you send a document for print, a book, or a number of pages that need to be sent to a client to review.
If you are using it for print, make sure you use the presets to correct DPI and compression on your images. Otherwise, clients may not be able to read any texts that you want them to review because it is compressed too much. Conversely, they may not have even received your file if it was too big for their email inbox.
When you save it as a PDF from Adobe Illustrator or Photoshop, they will have the ability to retain much of the editable capabilities of that file. If you have a Photoshop file where you save it as an Adobe PDF, be really aware of the file size. They can get huge! They will save all the layers, graphics, and text from allowing you to reopen it back up in Photoshop later on to re-edit.
We have found it more useful to save a PSD for Photoshop or Ai file for Adobe Illustrator than to save it as an Adobe PDF. Don’t retain the editing capabilities for printing since it really isn’t that useful. Unless the printing company specifically asks for that file type, avoid saving your file type as an editable PDF because the large file size will be cumbersome for opening and storing on your devices.