Text PDFs versus picture PDFs
There are two ways a browser can produce a PDF from a document, and the difference matters more than it sounds. The easy way renders the content to a canvas and drops that image into a PDF. It looks right on screen and is, functionally, a photograph: you cannot select the text, search it, copy from it, or have a screen reader read it. The file is also many times larger than it needs to be.
The other way writes real text runs into the PDF, positioning each line explicitly. That is what this tool does. The result is a small file whose content is genuinely text — which is what you want if the PDF will be read, archived, indexed, or passed through anything that extracts content from it.
What carries across
The DOCX is parsed into a document structure first, so headings stay headings, lists stay lists, and table rows stay together. Bold and italic emphasis is preserved. What is not preserved is anything tied to Word's own rendering: embedded fonts, images, columns, headers and footers, and exact page breaks.
For the reverse direction see PDF to Word. For plain text rather than a document, Text to PDF is simpler, and HTML to PDF takes markup directly.