Why do I get "Could not push back" error when trying to use the IBM Bluemix Document Conversion service?

I am trying to convert documents using the Bluemix Document Conversion service with a Node.js application. I am getting nothing but errors in my app, but the test document I'm using converts fine using the demo page. Below is a minimal app that demonstrates the problem (Note that, while this app is converting a PDF from disk, the "real" app can't do that, hence the Buffer object).

'use strict';

var fs = require('fs');
var DocumentConversionV1 = require('watson-developer-cloud/document-conversion/v1');
var bluemix=require('./my_bluemix');
var extend=require('util')._extend; //Node.js' built-in object extend function

var dcCredentials =  extend({
  url: '<url>',
  version: 'v1',
  username: '<username>',
  password: '<password>'
}, bluemix.getServiceCreds('document_conversion')); // VCAP_SERVICES
var document_conversion = new DocumentConversionV1(dcCredentials);

var contents = fs.readFileSync('./testdoc.pdf', 'utf8');

var parms={
   file: new Buffer(contents,'utf8'),
   conversion_target: 'ANSWER_UNITS',     // (JSON) ANSWER_UNITS, NORMALIZED_HTML, or NORMALIZED_TEXT
   content_type:'application/pdf',
   contentType:'application/pdf', //don't know which of these two works, seems to be inconsistent so I include both
   html_to_answer_units: {selectors: [ 'h1', 'h2','h3', 'h4']},
   };
console.log('First 100 chars of file:\n******************\n'+contents.substr(0,100)+'\n******************\n');
document_conversion.convert(parms, function(err,answerUnits)
   {
   if (!err)
      console.log('Returned '+answerUnits.length);
   else
      console.log('Error: '+JSON.stringify(err));
   });

The results from running this program against the test PDF (782K) is:

$ node test.js
[DocumentConversion] WARNING: No version_date specified. Using a (possibly old) default. e.g. watson.document_conversion({ version_date: "2015-12-15" })
[DocumentConversion] WARNING: No version_date specified. Using a (possibly old) default. e.g. watson.document_conversion({ version_date: "2015-12-15" })
First 100 chars of file:
******************
%PDF-1.5
%����
1 0 obj
<</Type/Catalog/Pages 2 0 R/Lang(en-US) /StructTreeRoot 105 0 R/MarkInfo<<
******************

Error: {"code":400,"error":"Could not push back 82801 bytes in order to reparse stream. Try increasing push back buffer using system property org.apache.pdfbox.baseParser.pushBackSize"}
$

Can someone tell me

1. How to get rid of the warning messages
2. Why the document is not getting converted
3. How do I "increase the push back buffer"

Other documents give different errors, but I'm hoping if I can make this one work then the other errors will go away too.

1. You can get rid of the warning message by specifying a version date in your configuration. See the tests for an example. 1

2. If the document converted through the demo but failed to convert when using your application, it is likely an error with how the binary data is passed to the service. (For example, it's getting corrupted or truncated.) You can see the Node.js source code for the demo here 2. It may help you figure out the mistake or give you a different approach to loading/sending the file.

3. That is an error from one of the underlying libraries used by the service. Unfortunately, it's not something that a caller can adjust at this point.