doc: keep pdftotext windows install instructions (partial revert #1515)

Author: terriko

test/README.md

@@ -145,3 +145,5 @@ pytest -v test/test_checkers.py -k python
 ```
 
 ## Known issues
+
+If you're using Windows and plan to run PDF tests, we **strongly** recommend also `pdftotext`. We experienced problems running tests without this. The best approach to do this is through [conda](https://docs.conda.io/projects/conda/en/latest/user-guide/install/windows.html) (click [here](https://anaconda.org/conda-forge/pdftotext) to find out how to install this package with conda).