Saving Photoshop master/working files in PDF, not PSD
A friend of mine uses PDF as the default format for saving Photshop files. For both master and working documents. He never saves anything as a PSD. Is this good practice?
Actually, you can save as PDF with Photoshop Editing Capabilities checked and retain most items.
The danger is, if as a PDF the file is opened in any other application and edited (or even saved) you may lose things without realizing it.
So, while it's certainly possible. It seems there's no valid reason to do so. I personally prefer double-clicking a Photoshop file and having it open in Photoshop, not Acrobat. I also need to keep track of actual PDF files compared to Photoshop files. How would one know the differences between a Photoshop PDF, Illustrator PDF, Indesign PDF, etc. It seems pure folly (or inexperience) to me.
In some cases people are just different to be different.
In general, as Scott says, it doesn't make a lot of sense to save PSDs as Photoshop PDFs. There is one important exception: if the file will be used in a layout (InDesign, for example) destined for print, and it contains vector information such as shape layers or type, then it should be saved in PDF format and placed in the layout as a PDF.
The reason this is a best practice is that when a PSD is placed in a layout program such as InDesign, what is actually placed is a rasterized composite. All vector art (at unlimited ppi) becomes raster art at whatever the image resolution happens to be at output, which would typically be 300 ppi for print. There is a world of difference between 300 ppi text and the 2800 dpi generated by an imagesetter or platesetter. A placed PDF retains vector information as vectors in the layout and when it is exported for press.
One of the more useful "minor" improvements in (if I recall correctly) InDesign CS5 was a change in the context menu to add "Edit Original with..." so that one could choose which program to use to open the linked file. A Photoshop PDF can then be opened in Photoshop for editing for a fast round-trip.