How can I add 4x5 300 dpi images to my website for download from clients without the images being enlarged on the website?
...without the images being enlarged
To me this implies that you do actually want to display these images, which the user wants to download anyway, but at normal size? With these being huge images they will naturally take a while to display, but you can just set a
width on the
img element and the browser will adjust the
height to the appropriate aspect ratio. The user then uses the context menu to save the image; just like any other image.
<img src="massive-300dpi-image.jpg" width="500" alt="Big Image">
However, if you do want to provide a download-only solution then see @Su' link in the comments.