Converting a document to PDF
Reproducing a document and converting it are different jobs. Only one of them can be done without sending your file somewhere.
"Convert this to PDF" sounds like one operation. It is two, they produce different files, and which one you want depends entirely on whether the layout is part of the content.
Reproducing, versus converting
Reproducing means the PDF looks exactly like the document did: the same fonts, the same line breaks, the same page breaks, the same everything. This is what you get from Print → Save as PDF inside Word, and it is exact because Word itself is doing the drawing — the program that laid the document out is the program producing the pages.
Converting means taking the content — the words, the headings, the lists, the emphasis — and setting it again. The result is a clean, correct PDF that does not match the original page for page. Nothing has been lost from what the document said; what has changed is where the lines and pages fall.
For a report, a letter, notes, a CV, minutes, an article, the difference rarely matters and the converted version is often tidier. For an invoice template, a certificate, a form, a poster, or anything where somebody positioned things deliberately, the layout is the content and only reproduction will do.
Why online converters need your file
This is the part worth understanding, because it explains an entire category of website. Reproducing a Word document faithfully means having Word's layout engine, or something that behaves like it. Nothing in a browser has one, and re-implementing it is a decades-long project that several companies have made their whole business.
So a service that promises a pixel-faithful conversion is running a copy of LibreOffice on a server. Your document is uploaded, opened by that software, printed to PDF, and sent back. That is not a criticism of how they work — it is the only way to get the result they promise. It does mean your document sits on somebody else's machine for a while, which for a contract, a medical letter or an unsigned agreement may be a bigger deal than the formatting was.
What our converter does instead
It reads the document in your browser, takes the structure out of it, and typesets a new PDF. Nothing is uploaded and nothing is stored. What survives is everything that was structural: heading levels, paragraph order, bulleted and numbered lists, bold, italic, inline code, tables as a plain grid, images scaled to fit, and block quotes.
What does not survive is everything that was presentational: page size and margins, columns, headers and footers, tab stops and hand-positioned indents, text boxes, shapes, charts and equations. Footnotes are dropped rather than dumped somewhere misleading. Merged table cells become a plain grid. And because the text is set in different fonts, every line break and page break falls somewhere new.
The text stays real text, incidentally — selectable, searchable, and readable by a screen reader. Some converters rasterise each page into an image, which looks right and is useless to anybody who needs to search it or hear it read.
The font limit, and the characters it stops
PDFs draw text with a font, and a font either travels inside the file or is assumed to be present in the reader. The fourteen standard PDF fonts are the ones every reader is guaranteed to have, and using them keeps the file small. They cover WinAnsi: English, the western European accented letters, curly quotes, dashes, the euro sign.
They do not cover Greek, Cyrillic, Chinese, Japanese, Korean, Arabic, Hebrew or emoji. A converter that ignores this fails partway through writing the file; ours counts and names the characters first, so you can decide before you commit. Supporting them properly means embedding a font that has them, which adds several hundred kilobytes to every PDF — the wrong trade for most documents, and the reason most tools quietly do not.
.doc and .docx are not the same thing
Despite the names, these are unrelated formats. .docx, from 2007 onward, is a zip archive of XML files — rename one to .zip and you can open it. That is why software other than Word can read it, and why our converter can.
.doc is the old binary format: a compound-document container whose specification was never fully published, and which is genuinely difficult to parse. Nothing in a browser reads it. If you have one, open it in Word, LibreOffice or Google Docs and save it as .docx — that conversion is free, exact, and takes a few seconds.
So which should you use?
If you have Word, LibreOffice or Google Docs open in front of you and the layout matters, print to PDF from there. It is exact, it is one dialog, and no tool can beat it.
Use a converter when you do not have the application — a .docx arriving on a phone or a Chromebook, or a Markdown file that no word processor made. Use ours specifically when the document is something you would rather not upload to a stranger, and when a clean re-typesetting is good enough for what you need. Those two conditions are the whole of its case, and it is worth being honest that they do not cover everything.