Does the problem happen with a particular PDF document or many PDF documents?
Would you press & hold over text to see if you can actually select the text?
If you are not able to select text, it means that your PDF document is likely a scanned PDF.
A scanned PDF document contains images of text, not real text. That's why Acrobat Reader cannot search for a word.
Would you try different PDF documents to see if Search works in Acrobat Reader for iOS?
Nah I'm not stupid I can select the text. Happens on all of them. Usually ctrl+F and I can find a word. How do I do it on the iPad?
You can tap the magnifier icon in the bottom bar to start search after you open a PDF document. (No keyboard shortcuts are available in Acrobat Reader for iOS on iPad/iPhone.)
Please take a look at the last section (titled: "Searching within a file") in the following online Help documentation for more details.