Recently, Safari released an update for their browser that now allows for the proper display of PDFs within iframes. However, back in the summer of 2011, this functionality was not available. It is important to use an ID when working with iframes.
<div id="scroller">
<iframe name="myiframe" id="myiframe" src="viewpdf-safari.php">
</div>
To ensure proper display, add the following CSS:
#myiframe {width:600px; height:100%;}
One issue you may encounter is that while the PDF will display within the iframe after the update, navigating through it can be difficult. Touch scrolling causes the entire iframe to scroll instead of just the PDF content, requiring two-finger scrolling. Other browsers handle this differently by properly filling the width of the iframe, unlike Safari at the moment. To provide a better user experience, consider adding a button or link to open the PDF directly in a new window to avoid this inconvenience.
An alternative solution is attempting to control the scrolling using the outer div as described in this resource, although I personally had difficulty implementing it successfully.