You can take a picture and turn it into a scanned PDF with Adobe Scan. Then you can open it with the Adobe Acrobat Reader DC app. You can also open a scanned PDF sent by your client. Adobe Acrobat Reader allows you to copy text from these documents to count words.
You need to put your finger at the beginning of a text fragment, drag it to the end, and then select the “Copy.” Unfortunately, in my version of the software, it was impossible to use the feature “Copy All” to copy the entire text at once without selecting it with a finger.