Pdf No response received

You used the wrong URL => For GET api calls the URL is always …/parse/imageurl - even if you want to OCR a PDF.

This link works:

https://api.ocr.space/parse/imageurl?apikey=helloworld&url=https%3A%2F%2Fdrive.google.com%2Fuc%3Fexport%3Ddownload%26id%3D18mRvhK_NuoLALCvERVwzLxu2xe-Fd-Q4