Why some PDF file don't work in PyPdf2 library?

Question

'''

PDFFILE=""
PDF_NAME=""
def pdf_btnClicked():
    global PDFFILE, PDF_NAME
    PathOfPDF = askopenfile()
    PDFFILE = PathOfPDF.name
    print(PDFFILE)
    if PDFFILE == "":
        return
    else:
        PDFLocation["text"] = PDFFILE
        # return PDFFILE
        # PDFFILE1=PDFFILE.get
        PDF_NAME= str(basename(normpath(PDFFILE)))
        print(PDF_NAME)
    
pages = 1
page_no = 1
pdfReader=''
def selectBtnClicked():
    global book
    global PDFFILE
    global pages
    global page_no
    global pdfReader
    print(PDFFILE)
    book = open(PDFFILE, 'rb')
    pdfReader = PyPDF2.PdfFileReader(book)
    pages = pdfReader.numPages
    print(pages)
    pages += 1
    page_no = [i for i in range(1, pages)]
    print(page_no)
    startfromLabel["values"] = page_no
    PDF_NAME_LABEL["text"]=PDF_NAME
    PDF_NAME_LABEL.place_forget()
    PDF_NAME_LABEL.pack(side=TOP, pady=20)
    startfromLabel.pack(side=TOP, pady=25)
    return page_no, pdfReader

def startBtnClicked():
    global pdfReader
    choice=startfromLabel.get()
    print(choice)
    speaker = pyttsx3.init('sapi5')
    voices = speaker.getProperty('voices')
    speaker.setProperty('voice',voices[1].id)
    page = pdfReader.getPage(int(choice))
    text = page.extractText()
    speaker.say("Thank YOU SIR, SELECTING ME FOR THIS JOB!!!")
    print("Thank YOU SIR SELECTING ME FOR THIS JOB!!!")
    speaker.say(text)
    print("Started")
    root.update()
    speaker.runAndWait()

'''

I had made a pdf describer using PyPdf2 in python. But I face a problem i.e it works in some pdf properly but in some other pdf file it doesn't work

problem example:-

it works properly on oop.pdf but it doesn't work on the_portrait_of_mr._w.h.pdf

Please help me to solve this problem

Thanking you