Neither the Find nor the Search feature works in Adobe reader (the relevant document was downloaded from an online database -- perhaps Academic Search Premier or Ebscot -- I do not recall). A message is returned that word is not found even for a word that I know is in the document. These tools are needed for reviewing documents of hundreds of pages.
If the file is a scanned images of pages, then the words are not really in the pdf file only a picture of the word.
Can you select a word and copy it into a text editor?