The document engine

By the end of this page you'll understand the one-time download that Office conversions need.

Office to PDF and Office Converter convert Word, Excel, PowerPoint, and OpenDocument files using LibreOffice (document engine) — a bundled engine that is downloaded once, on demand, rather than shipped inside the installer. That keeps the installer small for people who only work with PDFs and images.

What you'll see

The first time you convert a format that needs it, the panel shows Install LibreOffice (document engine) with a size and the note "one-time download — checksum-verified before use." Click Install, and a progress bar reports Downloading…, Verifying…, and Extracting….

It is roughly half a gigabyte, so give it a few minutes on a slow connection. It is verified against a known checksum before it is ever run, and kept for every future conversion.

Utilities that don't need it — PDF Converter, Image to PDF, PDF Organizer, PDF Tools, PDF Fill and Sign — never show this step. Neither do HTML and EPUB conversions in Office to PDF.

What usually goes wrong

If the install fails, the panel shows the error and the button becomes Retry. A failure is almost always the network or disk space; the download resumes from scratch, so make sure there's room for it first.