Vertically aligning CSS :before and :after content [duplicate]

I am trying to centre the link with the image, but can't seem to move the content vertically in any way.

<h4>More Information</h4>
<a href="#" class="pdf">File Name</a>

The icon is 22 x 22px

.pdf {
    font-size: 12px;
}
.pdf:before {
    padding:0 5px 0 0;
    content: url(../img/icon/pdf_small.png);
}
.pdf:after {
    content: " ( .pdf )";
    font-size: 10px;
}
.pdf:hover:after {
    color: #000;
}

Answered my own question after reading your advice on the vertical-align CSS attribute. Thanks for the tip!

.pdf:before {
    padding: 0 5px 0 0;
    content: url(../img/icon/pdf_small.png);
    vertical-align: -50%;
}

I'm no CSS expert, but what happens if you put vertical-align: middle; into your .pdf:before directive?

You can also use tables to accomplish this, like:

.pdf {
  display: table;
}
.pdf:before {
  display: table-cell;
  vertical-align: middle;
}

Here is an example: https://jsfiddle.net/ar9fadd0/2/

EDIT: You can also use flex to accomplish this:

.pdf {
  display: flex;
}
.pdf:before {
  display: flex;
  align-items: center;
}

Here is an example: https://jsfiddle.net/ctqk0xq1/1/

I think a cleaner approach is to inherit the vertical alignment:

In html:

<div class="shortcut"><a href="#">Download</a></div>

And in css:

.shortcut {
    vertical-align: middle;
}
.shortcut > a:after {
    vertical-align: inherit;
{

This way the icon will align properly in any resolution/font-size combination. Great for use with icon fonts.