Why your document prints inconsistently

Every page in a PDF carries its own dimensions. There is no document-level page size, and nothing requires the pages to agree.

This is genuinely useful — a report can hold a fold-out chart, a bound volume can include an A3 plan — and it is the reason documents assembled from several sources print in ways nobody expects.

How a document ends up mixed

You rarely choose this. It accumulates.

• A report written in A4, merged with a specification exported by an American office in Letter.
• A scan where the feeder pulled two sheets through slightly askew and the driver auto-cropped each page to what it found.
• A signed page printed, signed, scanned and reinserted, now a couple of millimetres different from its neighbours.
• A chart exported at whatever size the charting tool defaults to.

Onscreen this is nearly invisible. Readers scale each page to the window, so a document with four sizes in it looks perfectly uniform as you scroll.

What it breaks

• Printing. Drivers pick a paper size per job, not per page. Pages that do not match get scaled, centred or cropped, and which of those happens depends on the driver.
• Booklets and imposition. Placing two pages on a sheet requires knowing how big they are. Mixed sizes give inconsistent margins, or content running into the fold.
• Page numbers and headers. Anything positioned relative to a page edge sits differently on differently sized pages. A footer twenty-eight points from the bottom is in a different visual position on a page that is thirty points shorter.
• Binding. A stack that is not uniform does not trim cleanly.

Orientation is the same problem, sideways

A document mixing portrait and landscape is normal and usually intentional. A document where three pages are landscape *by accident* — because a scanner detected the wrong orientation — is a different matter, and produces the same class of surprise.

Worth distinguishing before normalising: unifying sizes should generally keep a deliberately landscape page landscape, and only make the footprint consistent.

Normalising, and when not to

Making every page the same size means scaling each one to fit and centring it. Content is never cropped; oversized pages come down, undersized pages go up, and proportions are preserved so nothing is stretched.

The trade is that a page scaled up from a smaller original is not sharper for having been enlarged, and a fold-out chart flattened to A4 may become unreadable. Normalise when a document needs to print predictably. Do not normalise when the varied sizes are the point.

The check worth doing first

Inspect the document and look at how many distinct page sizes it contains. If the answer is one, printing problems are elsewhere. If it is four, you have found the cause, and you can decide deliberately rather than discovering it at the printer.