You will need a vector to cut, and unfortunately it sounds like you only have rasters.
PDF is a container file; it can hold both vectors and rasters. It does not convert a raster to a vector just by saving it in PDF format. You will have to vectorize the PNG in some way.
If you already have Photoshop, you may also have Adobe Illustrator, which has a function called Image Trace that will help you do what you want… although some tutorials may be required, and sometimes the automatic functions don’t have quite the desired result.
Adobe Capture is a mobile companion app that has a quick vector function called Shapes, which could work also.
If you don’t have illustrator, Inkscape is free and has a similar set of features.
This thread has an awkward/too-fast video I made on the subject, and a link to a more detailed tutorial as well: Just Illustrator / Quick Vector Outline for cutting