>> require 'pdf/reader'
=> true
>> receiver = PDF::Reader::RegisterReceiver.new
=> #<PDF::Reader::RegisterReceiver:0x00000100a5b5a0 @callbacks=[]>
>> pdf = PDF::Reader.file("somefile.pdf", receiver)
TypeError: can't convert nil into String
	from /opt/local/lib/ruby/gems/1.9.1/gems/pdf-reader-0.8.5/lib/pdf/reader/parser.rb:140:in `block in hex_string'
	from /opt/local/lib/ruby/gems/1.9.1/gems/pdf-reader-0.8.5/lib/pdf/reader/parser.rb:137:in `loop'
	from /opt/local/lib/ruby/gems/1.9.1/gems/pdf-reader-0.8.5/lib/pdf/reader/parser.rb:137:in `hex_string'
	from /opt/local/lib/ruby/gems/1.9.1/gems/pdf-reader-0.8.5/lib/pdf/reader/parser.rb:55:in `parse_token'
	from /opt/local/lib/ruby/gems/1.9.1/gems/pdf-reader-0.8.5/lib/pdf/reader/content.rb:362:in `content_stream'
	from /opt/local/lib/ruby/gems/1.9.1/gems/pdf-reader-0.8.5/lib/pdf/reader/content.rb:316:in `block in walk_pages'
	from /opt/local/lib/ruby/gems/1.9.1/gems/pdf-reader-0.8.5/lib/pdf/reader/content.rb:314:in `each'
	from /opt/local/lib/ruby/gems/1.9.1/gems/pdf-reader-0.8.5/lib/pdf/reader/content.rb:314:in `walk_pages'
	from /opt/local/lib/ruby/gems/1.9.1/gems/pdf-reader-0.8.5/lib/pdf/reader/content.rb:296:in `block in walk_pages'
	from /opt/local/lib/ruby/gems/1.9.1/gems/pdf-reader-0.8.5/lib/pdf/reader/content.rb:296:in `each'
	from /opt/local/lib/ruby/gems/1.9.1/gems/pdf-reader-0.8.5/lib/pdf/reader/content.rb:296:in `walk_pages'
	from /opt/local/lib/ruby/gems/1.9.1/gems/pdf-reader-0.8.5/lib/pdf/reader/content.rb:283:in `document'
	from /opt/local/lib/ruby/gems/1.9.1/gems/pdf-reader-0.8.5/lib/pdf/reader.rb:134:in `parse'
	from /opt/local/lib/ruby/gems/1.9.1/gems/pdf-reader-0.8.5/lib/pdf/reader.rb:76:in `block in file'
	from /opt/local/lib/ruby/gems/1.9.1/gems/pdf-reader-0.8.5/lib/pdf/reader.rb:75:in `open'
	from /opt/local/lib/ruby/gems/1.9.1/gems/pdf-reader-0.8.5/lib/pdf/reader.rb:75:in `file'
	from (irb):3
	from /opt/local/bin/irb:12:in `<main>'