Separate Sections in a Built PDF

A document tells you a new section has started in one of three ways: the text gets bigger, the space gets wider, or a line appears. The document builder gives you all three. The interesting question is not how to draw a rule, which takes about four seconds, but when drawing one is the wrong answer.

A Divider is a real drawn line: a vector rectangle with its own thickness, width and colour, painted into the page rather than typed into it. That matters more than it sounds. The common alternative is a row of underscores inside a text block, and a row of underscores re-wraps the moment the typeface, the size or the margins change, usually into two ragged lines that nobody notices until the document has been sent.

• Thickness in points, from a quarter of a point up to twelve. The default is 1 pt, which reads as a line rather than a band.
• Width as a percentage of the text column, from 5 to 100, so a short centred rule is a setting rather than a guess.
• Alignment, left, centre or right, which only starts to matter once the width is below full.
• Colour, defaulting to a mid grey rather than black, because a separator should not be the darkest thing on the page.

The spacing around it is not yours to set, and it is already generous. A rule gets four points of clearance on each side of itself, on top of the ten points the block above it has already left behind, and another ten below. That is what stops it reading as an underline stuck to the end of the previous paragraph.

The useful rule of thumb is that a line marks a change of kind, not a change of topic. A heading already handles a change of topic, and it handles it better, because a heading also tells the reader what the new topic is. A line says only that something has ended.

• Between the letterhead and the body of a letter, where the sender's details stop and the message starts.
• Between the detail of an invoice and its payment terms, which are two different kinds of statement about the same job.
• On a form, where the line marks the boundary between what the applicant fills in and what the office fills in.
• Above a signature block, where the line is the thing being signed on rather than a separator at all.

What those share is that the reader is crossing a boundary, not turning a page in the same story. Everywhere else a rule is competing for attention with the content it was meant to organise, and it usually wins.

Whitespace is the only separator that never competes with the content, and it is the one most people reach for last. A Spacing block of 18 to 36 points between sections reads unmistakably as a break while adding no marks to the page. On anything that will be printed, it is also the separator that survives a tired photocopier, which a quarter-point grey line does not.

Space and a heading together are stronger than either alone, and stronger than a rule. Put 18 points above a Heading 2 and the section start is visible from across the room, which is roughly the test: scroll the preview out until the words are too small to read and see whether the shape still tells you where things begin.

Past three or four pages the problem stops being separation and becomes navigation. Two settings in the setup pane help more than anything you can do inside the blocks themselves, and both are off until you ask for them.

• Page numbers. Pick a corner or a centre, top or bottom, and a format: a plain number, Page 1, or 1 of 4. The last of those is the one that tells a reader holding a printout that a sheet has gone missing, and there is a separate option to leave the first page unnumbered.
• A reusable header or footer. One line repeated on every page, with {page} and {pages} filled in live at export. A checkbox decides whether they appear on the first page, which a title page or a covering letter usually does not want.

The third thing is less of a setting and more of a discipline: keep the mapping between heading levels and meaning stable for the whole document. Nothing in the builder enforces it. A document where Heading 2 means a section in the first half and a subsection in the second is genuinely harder to read than one with no headings at all, because the reader has learned a rule that then stops being true.

1. 1

   Start with a heading

   It separates and it labels. If a section deserves a break it usually deserves a name, and a name is worth far more to the reader than a line is.

2. 2

   Add space when the heading is not enough

   A Spacing block above the heading turns a size change into a section start. This is the step most documents are missing, and it is the cheapest one to add.

3. 3

   Draw a rule only where the kind of content changes

   Letterhead to body, detail to terms, applicant to office. If you cannot name the boundary the line is marking, the line is decoration and the document is better without it.