Slug line and sheet numbering

Both of these controls put text on the sheet that is never meant to survive the job. The slug line carries job information for the people handling the paper; sheet numbering counts the sheets so a pile can be checked. Both live outside the trim, and both are cut away in finishing.

They are also the two controls that make an imposed sheet self-describing. A sheet with a slug line and a number tells anyone who picks it up which job it belongs to and where it sits in the run. A sheet without them is an anonymous piece of paper, and in a shop running four jobs at once that is a real cost.

The slug line

The slug is off by default. Turn it on and it prints at an x and y position you set in millimetres, defaulting to 5 mm and 5 mm — that is, just inside the corner of the sheet, well outside the trim of any sensibly imposed block.

What you put in it is a shop decision rather than a software one, but the useful contents are consistent across every shop that bothers: the job or docket number, the customer, the file name, the stock, the date and time of imposition, and the operator. The purpose is to make it impossible to confuse two piles of paper, and every field you leave out is a way for that to happen.

Sheet numbering

Numbering has more parameters than the slug, and each one does something specific.

Zero-padding matters more than it looks. A padded number is a fixed-width column: stood on end, a padded stack shows a straight edge of digits and a single misfiled sheet is visible from a metre away. An unpadded stack going 8, 9, 10, 11 shifts every character position as it crosses each power of ten, and the eye has nothing to lock on to.

Using sheet numbers to check a stack

The reason to number sheets is not decoration. It is that a printed pile has to be verified as complete and in order at two moments — after the press and after the guillotine — and a number is the only thing that makes that verification quick.

1. Off the press, fan the pile and read the numbers. They should run without a gap. A missing number is a misfeed nobody noticed; a repeated number is a reprinted sheet that went back into the pile in the wrong place.
2. Before the knife, confirm the top sheet is the number you expect. If the delivery reversed the stack, the pile is in the opposite order, and for Cut & Stack work that inverts the whole sequence.
3. After the knife, the numbers are on the waste. That is the point — the check happens while the evidence still exists, and it is thrown away with the offcut.

For sequential work this check is not optional. Cut & Stack guarantees the finished order only if the sheets went through in press order, and sheet numbers are the only cheap way to know that they did.

Why numbering is refused in Booklet mode

Set numbering on a Booklet job and it is rejected with Numbering is unavailable in Booklet mode. This is not an oversight, and it is not a feature waiting to be built.

Everything above depends on one assumption: that the area outside the trim becomes waste. On a flat sheet trimmed into pieces, that is true — the number is printed on the offcut and leaves with it. A folded signature does not work that way. The sheet is folded first and trimmed as a single made-up piece afterwards, and the three trimmed edges of a folded section are the head, the foot and the fore-edge of the finished book. There is no fourth waste edge on a flat sheet to put a number on, because after folding, every part of that sheet is either inside the book or one of the three trimmed edges.

Put a number 5 mm from the corner of a sheet that is about to be folded twice and it lands on a page. Not on a waste strip: on page 3, or page 6, in the finished booklet. The choice was between printing it where it cannot be removed and refusing the combination, and refusing is the honest option.

The slug line remains available in Booklet mode, and it has the same problem in principle — so position it deliberately, print one section, fold it, and look. See Booklet imposition for how the folded sheet is laid out.

Common mistakes

Placing the slug or number inside the trim

The coordinates are yours to set and nothing stops you putting them under the block. The result is job information printed across the artwork on every piece. Before exporting, check that the position you chose is outside the outermost trim edge — and remember the crop marks are already claiming 8 mm out there. See crop marks.

A numbering quantity that does not match the sheet count

Quantity defaults to 100. If your job is 240 sheets, the last 140 come out unnumbered and the completeness check silently stops working two-thirds of the way through the pile. Work out the sheet count from the imposition — pages divided by positions, halved again if duplexed — and set the quantity to match.

Turning zero-padding off

It looks tidier on a single sheet and it defeats the purpose on a stack. The fixed-width column is the whole reason a fanned pile can be checked at a glance. Leave padding on unless something downstream is reading the numbers and cannot cope with them.

Numbering the face nobody will look at

Face defaults to Front. If the pile is delivered face down, the numbers are underneath and the operator turns the whole stack to check it — which is itself a chance to reverse the order. Decide which side the number should be on for the way your press delivers.

Checking the numbers after the guillotine

By then they are in the bin. The number exists to be read while the sheet is still whole. Build the check into the moment the pile comes off the press, not into the moment somebody notices a problem.