My first thought is why aren’t these files print-ready when you receive them?
If they’re being supplied as final production artwork, there’s really no excuse for them not being set up correctly in the first place. I’d be questioning why these problems are getting through before they even reach you.
For the dieline, I’d have it on its own layer, using a clearly named spot colour, set to overprint. In my view, it should be the uppermost layer in the stack so it’s always visible and easily identified. Setting to overprint ensures it doesn’t knock out any artwork underneath.
Missing fonts?
How are you receiving these files? If they’re print-ready PDFs, the fonts should already be embedded (or outlined where required).
Are you opening the supplied PDFs in Illustrator? If so, I’d stop doing that straight away.
Illustrator, or any other vector editing software, isn’t a general-purpose PDF editor. Unless the PDF was created in Illustrator with its editing capabilities preserved, reopening it can introduce problems that weren’t in the original PDF.
I’d be checking the supplied PDFs in Acrobat Pro rather than opening them in Illustrator.
Apologies if you’re not doing this, but I’ve seen it before and this kinda sounds like it.
Low-resolution images?
If you’re talking about low-resolution images in the printed artwork, that’s straightforward enough to identify through preflight. But again, why are they being supplied to the artworker, and ultimately you, in that state?
Unlabelled spot colours?
That’s a recipe for disaster.
Every separation should be clearly identified with the correct spot colour name, and that naming should match the printer’s specifications. I’d also check that the spot colours really are defined as spots, haven’t been converted to process and aren’t producing unexpected additional plates.
Foil, UV and embossing
These should have their own clearly identified separations.
Generally, spot UV is set to overprint, and foil often is too, but I’d be careful making that a blanket rule. Hot foil, cold foil and digital foil can have different requirements, particularly when it comes to knocking out the underlying print.
I’d be following the printer’s specifications rather than assuming everything must overprint.
Checking the separations
This is where I’d spend most of my time.
In Acrobat Pro, go to Print Production > Output Preview.
Select Separations and toggle the individual plates on and off. Check each separation independently, particularly where different finishes overlap the printed artwork.
You can toggle Simulate Overprinting on and off to see how the PDF behaves. (Good for finding white text set to overprint)
In the same window, change the preview to Color Warnings and tick Show Overprinting . This highlights objects set to overprint and makes it much easier to identify something that shouldn’t be.
I’d also be checking for stray objects, unexpected knockouts, missing elements and anything appearing on the wrong separation.
Beyond that, I’d be looking at registration tolerances, minimum line weights, fine details, bleed, folds and whether foil or UV is too close to cutting or creasing areas. Glue flaps and varnish-free areas are worth checking too, depending on the packaging.
The automation side of things is interesting.
Automated preflight is excellent for catching technical problems. Missing fonts, low-resolution images, incorrect spot colours and similar issues are relatively easy to flag.
But how does the tool know that an area should be foiled, knocked out or overprinted in the first place?
That’s where I’d still want a visual check against an approved reference. A separation can be technically perfect and still be completely wrong if the artwork itself hasn’t been interpreted correctly.
And an Acrobat preview isn’t necessarily a substitute for checking the final RIP output or getting an appropriate production proof.
Out of curiosity, what tool have you built? Is it working from native artwork files to generate the separations, or are you feeding it supplied PDFs and having it generate the plates from those?