using pdf-image with firebase functions and firebase storage

[neo-xy]

Looking very much for some guidance here - after uploading my pdf file to firebase storage a function in my firebase functions (node-typescript) is called where I'm getting a downloadUrl to file.

I tried to pass that when creating an instance of PDFImage as
let pdfImage = new PDFImage(downloadUrl)

...and then just using:
pdfImage.convertFile()

..like shown in documentation, but it does not works (maybe 'downloadUrl can not be used there...?)

(the objective is to convert pdf to images and save those in firebase storage );
Does anyone have any suggestion on how to tackle that problem?:S
best regards