Adobe Acrobat XI

If you purchased it as a download it might still be available under your Adobe account as a downloadable link. I don't believe it's available on their normal web-site any longer, as this is a very old, unsupported version.

You should also know that it's not compatible with any current OS. To increase the chances of it working properly make sure you have all updates installed (up to 11.0.23) and run it in Compatibility Mode with an earlier OS, like Windows 7.

Updates are available here:
ftp://ftp.adobe.com/pub/adobe/acrobat/win/11.x/
You must use a dedicated FTP client to open the link, it won't work in most browsers.