Bootstrap: vertically align paragraph text and buttons

Using the same styling as the .btn would probably be a good approach. Example with disabled .btn

<p>
    <a class="btn btn-default" href="#">Take exam</a> 
    <span class="text-muted btn" disabled="true">Text</span>
</p>

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Or make a class of .btn-align with the same attributes. Example

CSS

.btn-align {
    padding: 6px 12px;
    line-height: 1.42857143;
    vertical-align: middle;

}

HTML

<p>
  <a class="btn btn-default" href="#">Take exam</a> 
  <span class="text-muted btn-align">Available after reading course material</span>
</p>

In Bootstrap 4, you can do this using utilities to set display: inline-block and vertical-align: middle in case you don't want to create a special CSS class for it.

<p>
    <a class="btn btn-outline-secondary" href="#">Take exam</a> 
    <span class="text-muted d-inline-block align-middle">Available after reading course material</span>
</p>

Example