How do I make a WordPress PDF fit on one page?

Use the setting that matches what you mean by one page. A printable A4 or Letter page and one long page without page breaks need different settings.

Fit everything onto one printable page

If the output must be one normal printable page, first set the Page Size option to A4 or Letter.

Then set the Content Fit Mode option to single-page-ratio or single-page. This tells the converter to fit the page content into the print area of one page.

Use this only when the result remains readable. A long WordPress page can become very small when it is forced onto one A4 or Letter page.

Create one long page without page breaks

If you do not need a normal printable sheet and only want to avoid page breaks, set the Page Height option to -1. This creates one page that expands vertically to fit the content.

Use this for web pages, reports, or screenshots where one continuous page is more important than paper printing.

Adjust layout before forcing one page

If the content almost fits, adjust the Content Viewport Width option before forcing a very small scale. A wider viewport can make some pages use fewer lines and fit better.

Use the Scale Factor option only when the layout is otherwise correct and the content just needs to be slightly smaller or larger.

Do not use Page Layout for this

The Page Layout option controls how a PDF viewer displays pages after the file is opened. It does not make the document contain only one page.

If the problem is page breaks, not one-page output

If you need normal multi-page output but page breaks, blank pages, or cut-off content look wrong, use the layout FAQ instead: How can I fix WordPress PDF layout, page size, or page breaks?.