Adobe Acrobat Reader DC continuous release version 2018.009.20050 question: How to make "non-word-searchable" pdf files "word-searchable"?

Hi,

I would need information on Adobe Acrobat Reader DC continuous release version 2018.009.20050. There are certain pdf files from my online college classes which I can't do word search in with this Adobe version of mine. Is there any way to fix this? In other words, is it possible to make these pdf files "word-searchable"?

Thanks!

Edita