programmatically rename file in ocrmyfile - pdf

Question

I'm a new programmer and I'm making a first attempt at a larger data science project. To do this I have made a class that is supposed to open PDFs with ocrmypdf and then uses a while statement to walk through all the documents in a folder.
class DocumentReader:
This class is used to open and read a
# document using OCR and then
# creating the document in its place
def __init__(self,file):
self.file = file
def convert(self):
ocrmypdf.ocr(self.file,new_doc,deskew=True)
and here is the while statement:
count = 0
while count <final:
for file in os.listdir('PayStubs'):
if file.endswith(".pdf"):
index = str(file).find('.pdf')
new_doc = file[:index]+'_new'+file[index:]
d1=DocumentReader(file)
d1.convert()
I can make each of the classes work if I run them individually but it is the '.pdf' extension when I try to run them programmatically that is messing me up. Does anyone know how to create a new file name programmatically for the second argument in the ocrmypdf command?
I have tried several different ways of making this work but I keep getting errors. The most common errors that my attempts have yielded are:
InputFileError: File not found - 20070928ch6495.pdf.pdf
and
isadirectoryerror: [errno 21] is a directory: '_new/'
I'm to the point where I'm running in circles. Any help would be greatly appreciated. thanks!