Changing the extension does not make it a PDF. How to check file types in Windows 11

You were asked to "send it as a PDF," so you changed the end of the filename from ".docx" to ".pdf" and sent it. However, the ...
Houston Chronicle

Can I Convert a PDF to a Tax Exchange Format?

Tax Exchange Format, or TXF, is an extension for files containing tax-related data such as income, expenses and stock transactions. This standard file format is supported by several financial software ...

This free Windows tool lets me convert almost any file to another format – here's how

With the free File Converter program, you can easily convert images, videos, and audio files to other formats.
Linux Journal

OpenOffice.org: Sun PDF Import Extension

The Sun PDF Import Extension is one of the most popular OpenOffice.org extensions ever created. For the last two years, it has been near the top of the list of most popular downloads on the OpenOffice ...