UnicodeDecodeError: 'charmap' codec can't decode byte 0x8d in position 386: character maps to <undefined>

I'm trying to read a pdf file with the slate library but it throws this error:

import slate

pdf = 'tabla9.pdf'

with open(pdf,encoding="utf-8") as f:

doc = slate.PDF(f)

for page in doc[:2]:
   print(page)

complete error:

File "C:\Users\user\libro5.py", line 7, in <module>
doc = slate.PDF(f)
File "C:\Python3\lib\slate\classes.py", line 52, in __init__
self.parser = PDFParser(file)
File "C:\Python3\lib\site-packages\pdfminer\pdfparser.py", line 646, in 
__init__
PSStackParser.__init__(self, fp)
File "C:\Python3\lib\site-packages\pdfminer\psparser.py", line 189, in 
__init__
PSBaseParser.__init__(self, fp)
File "C:\Python3\lib\site-packages\pdfminer\psparser.py", line 134, in 
__init__
data = fp.read()
File "C:\Python3\lib\codecs.py", line 322, in decode
(result, consumed) = self._buffer_decode(data, self.errors, final)
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xe2 in position 10: 
invalid continuation byte

classes.py, line 52:

class PDF(list):
    def __init__(self, file, password='', just_text=1, check_extractable=True, char_margin=1.0, line_margin=0.1, word_margin=0.1):
        self.parser = PDFParser(file)

pdfparser.py, line 646:

def __init__(self, fp):
        PSStackParser.__init__(self, fp)

psparser.py, line 189:

class PSStackParser(PSBaseParser):

    def __init__(self, fp):
        PSBaseParser.__init__(self, fp)

psparser.py, line 134:

class PSBaseParser:

    """Most basic PostScript parser that performs only tokenization.
    """
    def __init__(self, fp):
        data = fp.read()

File "C:\Python3\lib\codecs.py", line 322, in decode (result, consumed) = self._buffer_decode(data, self.errors, final) UnicodeDecodeError: 'utf-8' codec can't decode byte 0xe2 in position 10: invalid continuation byte:

def decode(self, input, final=False):
    # decode input (taking the buffer into account)
    data = self.buffer + input
    (result, consumed) = self._buffer_decode(data, self.errors, final)

I'm using Python 3.7 on Windows 10.

A PDF file is binary, it's inappropriate to open it in text mode with an encoding.

Try:

with open(pdf, "rb") as f: