[SalesForce] Bootstrap not working in PDF rendering

Following is my code which is working fine as a VF page on preview, but no styling adding on rendering as PDF renderAs="PDF". Let me know what I am doing wrong as I am new to the platform.

Code –

<apex:page>
  <!-- Adding CSS -->
  <!-- <apex:stylesheet value="{!URLFOR($Resource.SLDS092, 'assets/styles/salesforce-lightning-design-system-vf.css')}" /> -->

<!-- Latest compiled and minified CSS -->
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap.min.css" />

<!-- Optional theme -->
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap-theme.min.css" />

<div class="container">
<div class="row">
  <div class="col-md-6">.col-md-6</div>
  <div class="col-md-6">.col-md-6</div>
</div>
<div class="row">
  <div class="col-md-8">.col-md-8</div>
  <div class="col-md-4">.col-md-4</div>
</div>
<div class="row">
  <div class="col-md-4">.col-md-4</div>
  <div class="col-md-4">.col-md-4</div>
  <div class="col-md-4">.col-md-4</div>
</div>
<div class="row">
  <div class="col-md-6">.col-md-6</div>
  <div class="col-md-6">.col-md-6</div>
</div>
</div>
</apex:page>

Best Answer

You're not going to be able to render PDFs properly that were created with Bootstrap. The Flying Saucer Render engine used by Salesforce only supports CSS 2.1 and HTML 4.1