Points, pitch and lines per inch

Peter Flynn peter at silmaril.ie
Sun Feb 9 23:31:11 CET 2020

On 09/02/2020 21:25, Djones9976 via texhax wrote:
> I specified arial 12pt in the preamble of my document.   But how can
> I control the pitch (i.e. characters per inch) 

Pitch only applies to monospace (typewriter-style) typefaces. In normal 
typefaces, including Arial, each character is a different width.

> and lines per inch in the document; 

By default, [La]TeX uses a line-height of 1.2 times the font size, so 
12pt type would typically be set on lines 14.4pt apart. With 72.27 point 
per inch, that's five lines per inch (actually 5.01875).

Warning: those are traditional Anglo-American printers' points. Most 
other typesetters nowadays use Adobe's "big points" with exactly 72pt to 
the inch. The difference is small, but in the typical height of an A4 or 
Letter page, it can add up to nearly ⅛" (3mm) which your clients will 
certainly notice and complain about if they measure the full page. In 
Adobe points, 72 ÷ 14.4 is exactly 5".

> or how can I tell what the pdf is being printed in?

Depending on who or what created the PDF this varies from hard to 
virtually impossible. If you have absolute confidence that your printer 
is printing exactly to scale, without enlarging or reducing, you could 
just measure the printout. I'm sure there is an internal setting in the 
PDF, which could possibly be more simply exposed by converting to 
Postscript, which is human-readable, but I've never needed to know it, 
because I am confident that LaTeX does the job correctly. Possibly the 
fully-paid version of Adobe Acrobat could show this.


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