Be careful. Today, there was a big "Start Download" with directions to download, install, start. This is a misleading, commercial link. To use the free service, click on "Chooose PDF/Browse" then "Convert" . On next page, click "View" and "Download". For converting topo maps, I found 150 dpi too coarse, but 300 dpi was good enough.

This site will sell or distribute any personal information contained in the documents you upload. Their privacy policy is simply a lie. I know this from personal experience. I uploaded a PDF resume file containing an email address that had never been used before, but had existed for 4 months prior. I am 100% positive it was compromised by this site. The address had never received any mail, and no mail was ever sent from the address. It had also never been displayed anywhere online. It was simply a dormant email address for 4 months. Within hours of using this site, I began to receive spam mail, and am now getting multiple spam emails every day. Use this site at your own risk - even if you upload a document containing no personal info, they may be able to strip meta data.