pdfposter hangs in 18.04

[Brian Wharton]

Just installed version 0.6.0 from the repository for 18.04 and when creating a poster the program just hangs, no msg, no output.
After a ctrl-c the following occured:

pdfposter --scale=4 Micro-Magic_Plan_2016_V2.pdf Plan.pdf
^CTraceback (most recent call last):
  File "/usr/bin/pdfposter", line 9, in <module>
    load_entry_point('pdftools.pdfposter==0.6.0', 'console_scripts', 'pdfposter')()
  File "/usr/share/pdfposter/pdftools/pdfposter/cmd.py", line 129, in run
    main(opts, *args)
  File "/usr/share/pdfposter/pdftools/pdfposter/__init__.py", line 340, in main
    outpdf.write(open(outfilename, 'wb'))
  File "/usr/lib/python2.7/dist-packages/PyPDF2/pdf.py", line 501, in write
    obj.writeToStream(stream, key)
  File "/usr/lib/python2.7/dist-packages/PyPDF2/generic.py", line 785, in writeToStream
    self[NameObject("/Length")] = NumberObject(len(self._data))
  File "/usr/lib/python2.7/dist-packages/PyPDF2/pdf.py", line 2769, in _getData
    op.writeToStream(newdata, None)
  File "/usr/lib/python2.7/dist-packages/PyPDF2/generic.py", line 252, in writeToStream
    stream.write(b_(repr(self)))
  File "/usr/lib/python2.7/dist-packages/PyPDF2/generic.py", line 242, in __repr__
    o = "%.5f" % self
TypeError: float argument required, not FloatObject

I have the latest versions of python2 installed, and PyPDF2 is installed.