Just like you have "proxy" link for placed Photoshop.eps files - apply the same feature for PDFs. When PDFs are placed in IL as links, no-one needs hi-res preview of PDFs which causes super sluggish performance of IL. Anything you do in IL, is being slow cause that hi-res preview is on all the time. This feature allows you to place super big files (gigabytes) and handle them with ease. I just wish you can do this with PDF. All Adobe needs to do is use PDF thumbnail (option).