When a print PDF still carries its layers, they usually fall into five kinds. Knowing which is which tells you what you can recover, what each group is for, and which ones are worth paying attention to before you rebuild anything.
The names below are the ones PDFLayerExtract uses when it sorts detected groups. Other tools use other words for the same things, and the section on naming at the end covers the common variations.
Spot
A spot layer holds artwork that prints in a named ink rather than a CMYK mix: a brand Pantone, a metallic, a fluorescent. In a layered PDF it is usually a separate group so the prepress operator can check it, trap it and send it to its own plate.
If you are recreating a job and the spot layer is missing, you are guessing at which objects were meant to be the special ink. If it survived as an OCG, you get it back exactly as drawn.
Clear
Clear covers varnish, spot UV, gloss and matte coatings, and any other finish that prints on top of the artwork but is not itself artwork. It is almost always drawn as solid shapes on a separate layer, because it goes to a separate unit on the press or to a separate pass entirely.
Clear layers are the ones most often lost in a flat PDF, because on screen a varnish shape looks like nothing at all. In Acrobat’s Layers panel, toggling it usually shows a faint outline appearing and disappearing. That outline is the whole finish.
Cut
Cut is the dieline, the kiss-cut, the crease, the perforation and the bleed guide. It is drawn in a distinctive colour, often magenta or a named “Cutter” spot, and it must never print. It exists so the die maker and the finishing department know where the edges are.
A cut line embedded in a flat PDF is a trap: it looks like a magenta stroke, it prints like a magenta stroke, and someone has to find and remove it by hand. As a separate OCG it is one click to hide, one file to send to the die maker.
Print is the artwork itself: everything that goes to the CMYK plates or the digital press. In most layered PDFs this is the largest group, and often the only one that looks like a finished design when viewed alone.
The print layer is rarely the problem. It is what Illustrator shows you when it flattens the file. The problem is everything else that got merged into it.
Info
Info is job notes, registration marks, dimension callouts, colour bars, approval stamps and anything else that helps a person and must not reach the press. Some tools call this “Notes”, “Slug” or “Annotations”.
An info layer merged into the print artwork is how a proof stamp ends up on a thousand printed labels. Separated, it is the layer you hide before output and show when someone asks what the job was supposed to be.
How the types show up in practice
A typical label PDF from a CorelDRAW or AutoCAD export might carry all five. A packaging PDF from a prepress system might carry cut, print and a couple of clear layers with technical names. A simple flyer usually carries none, because there was never anything to separate.
The free check in PDFLayerExtract lists the groups it finds and assigns each to one of these five types based on the group’s name and content. Where a group cannot be classified with confidence, it is still listed and still extracted; it simply does not get a type label. The classification is there to help you read the list quickly, not to hide anything.
On naming
Groups are named by whoever exported the file, and the names vary. “Dieline”, “Cutter”, “Die”, “Kiss Cut” and “Cut Contour” are all cut. “Varnish”, “UV”, “Gloss”, “Spot Varnish” and “Coating” are all clear. “PMS 185”, “Metallic Silver” and “Spot 1” are all spot. “Notes”, “Slug”, “Marks” and “Do Not Print” are all info.
When you check a file in Acrobat, read the names but trust the toggles. A layer called “Layer 3” that hides the cut line is a cut layer, whatever it is called.
What none of this recovers
Layer types describe groups that exist in the PDF. They cannot describe groups that were flattened away before export. If the Layers panel in Acrobat is empty, there are no types to find, and the file needs to be rebuilt or resourced. The check is free precisely so you can find that out before spending anything.