Edit>Find Search

What app is your work created in now? Most have than function built in so you do not beed a third-party app.

This is from searching an Apple support document for the word "rapid" using command f in Safari:

Textedit works the same way. So does Apple's Pages.

In Office Mac 2019, command f finds the first occurence but subsequent use of command g moves the highligh tothe next occurence.

With more detail from you I may be able to give more specific suggestions.

If you're looking for a single word the following probably won't work unless the word is a unique one:

1 - bring up the Spotlight search field with ⌘+Spacebar.

2 - enter the unique word or phrase in quotes:

That will find all documents in which that phrase is located.

Preview (pretty much all Apple apps) will recognize text in a picture of a document. I get mixed results, but maybe that's all you need.

You would need Optical Character Recognition (OCR) software to convert the picture of text to text.