Whitespace gone from PDF extraction, and strange word interpretation

Without using the PyPdf2 use Pdfminer library package which has same functionality, as bellow. I got the code from this and as i wanted I edited it, this code gives me a text file which has white-space among words. I work with anaconda and python 3.6. for install PdfMiner for python 3.6 you can use this link.

from pdfminer.pdfinterp import PDFResourceManager, PDFPageInterpreter
from pdfminer.converter import TextConverter
from pdfminer.layout import LAParams
from pdfminer.pdfpage import PDFPage
from io import StringIO

class PdfConverter:

   def __init__(self, file_path):
       self.file_path = file_path
# convert pdf file to a string which has space among words 
   def convert_pdf_to_txt(self):
       rsrcmgr = PDFResourceManager()
       retstr = StringIO()
       codec="utf-8"  # 'utf16','utf-8'
       laparams = LAParams()
       device = TextConverter(rsrcmgr, retstr, codec=codec, laparams=laparams)
       fp = open(self.file_path, 'rb')
       interpreter = PDFPageInterpreter(rsrcmgr, device)
       password = ""
       maxpages = 0
       caching = True
       pagenos = set()
       for page in PDFPage.get_pages(fp, pagenos, maxpages=maxpages, password=password, caching=caching, check_extractable=True):
           interpreter.process_page(page)
       fp.close()
       device.close()
       str = retstr.getvalue()
       retstr.close()
       return str
# convert pdf file text to string and save as a text_pdf.txt file
   def save_convert_pdf_to_txt(self):
       content = self.convert_pdf_to_txt()
       txt_pdf = open('text_pdf.txt', 'wb')
       txt_pdf.write(content.encode('utf-8'))
       txt_pdf.close()
if __name__ == '__main__':
    pdfConverter = PdfConverter(file_path="sample.pdf")
    print(pdfConverter.convert_pdf_to_txt())