A mounting and proofing apparatus has plate and layout cylinders rotatably mounted in a frame in parallel alignment to each other. A partial mirror is disposed proximate the plate and layout cylinder to permit a user looking into the partial mirror to view superimposed images of the layout and plate cylinders. At least one video camera is disposed above and directed at the partial mirror to image the superimposed images upon a video display having radicle markings. A layout sheet is installable on the layout cylinder indicating proper positioning of printing plates on the plate cylinder. The video camera optionally magnifies superimposed images of registration marks on the layout sheet and the plate cylinder. The user aligns the radicle with the registration mark, places a printing plate on the imaged area of the plate cylinder, and then aligns corresponding registration mark on the printing plate with that of the layout sheet. The magnification is sufficient to allow alignment of microdot registration marks on flexographic printing plates. Encoders allow a digital readout of camera positions and circumferential displacement of the plate and layout cylinders facilitating alignment verification and location of registration marks on the layout sheet. Optionally, the magnification of the video displays of the cameras may be altered optically or electronically to increase a field of view to allow alignment of printing patterns, and in particular those of slug plates, without the use of registration marks.