How to check a PDF against PDF/X or PDF/UA rules

Open Layout by Zaweba and choose File > Check a PDF. Point it at any PDF, whether Layout made it or not, and it checks the file against the rules of PDF/X-1a, PDF/X-3, PDF/X-4, PDF/A-2b and PDF/UA-1, then shows the document's structure tree. It is a practical check rather than a certified validator, so treat it as a strong first pass and still let the printer or the accessibility reviewer have the final say.

That distinction matters, so it is stated plainly in the app. A certified validator is a tool that an industry body or a buyer has agreed to trust. Check a PDF is there so you can find the problems yourself, early, before a file goes out and comes back rejected.

What the different standards are for

PDF/X is a family of rules for print. The idea is a file that leaves nothing to guesswork at the press: fonts embedded, colours defined, nothing that depends on the screen. X-1a is the strictest about colour and suits jobs printed entirely in CMYK. X-3 allows colour-managed data. X-4 allows live transparency and is the usual modern choice when a printer accepts it. PDF/A-2b is about long-term archiving, so a file opens the same way in years to come. PDF/UA-1 is about accessibility, so screen readers and other assistive tools can read the document in a sensible order with headings, alt text and table structure.

Which one to check against depends on where the file is going. A print shop will normally tell you which PDF/X flavour it prefers. A public body or a publisher may ask for PDF/UA. An archive may want PDF/A.

Running the check

Choose File > Check a PDF and open the file. Read the results for the standard you care about. Each finding tells you which rule was not met. For accessibility, the structure tree is the most useful part of the window, because it shows what a screen reader would actually meet: whether the headings are tagged as headings, whether pictures carry alt text, and whether the reading order matches the page.

If the PDF came from Layout, the fix is usually back in the document rather than in the PDF. Missing alt text is added to the picture, a wrong heading level is fixed through the paragraph style's export tagging, and colour problems go back to the swatches or the colour settings. Then export again and check again. Repeat until the list is clean for the standard you are aiming at.

If the PDF came from somewhere else, the check still tells you what is wrong, which is useful when you are deciding whether a supplied advert or a client's file can go to press as it is.

Making files that pass first time

Export presets do a lot of the work. Layout's PDF export has presets named after the standards: PDF/X-1a-style, PDF/X-3-style, PDF/X-4-style, PDF/A-2b-style and Accessible (PDF/UA style), alongside High quality print, Press quality, Smallest file and Interactive. The "style" in those names is honest: they set the file up the way the standard expects, and Check a PDF is how you confirm the result.

Live preflight inside the document catches much of the rest before you export: missing fonts and links, RGB pictures in a print job, low-resolution pictures, overset text and missing glyphs among them. There is an Accessible preflight profile too, which looks at the things PDF/UA cares about.

When to stop and ask

If the check is clean and the printer still raises a problem, believe the printer. Their workflow may test things no general rule covers, such as a particular ink limit or a maximum file size. If the check shows an issue you do not understand, the rule name in the result is the thing to search for or to quote back to whoever asked for the standard. Either way, you have the facts about your own file in a couple of minutes, without sending it anywhere.