If you are copying text directly from a website to paste into a plain text file, using the Reader View in your web browser can make this easier. This view strips away all the "junk" on a webpage and leaves you with the core text on the page. Reader View is a built in option in Safari [look for the icon directly to the left of the URL bar], Firefox [look for the icon at the far right end of the URL bar], and Microsoft Edge [look for the icon at the far right end of the URL bar]. An extension is available for Chrome.
If you are working with PDFs of text that you need to convert to .txt, you can use Adobe Acrobat (installed on all lab computers on campus) to do those conversions. This guide from Rowan University outlines the process. Note: Born digital PDFs will convert much more easily, and are usable in Voyant without the need to convert them. Scanned PDFs are more challenging to convert and work with -- you can ask Dr. Jakacki, Claire, or Carrie for help with these.