if you have acrobat standard, you need to get the installation file from the vendor you used.
if that's adobe, https://www.adobe.com/account.html
if that's dell, https://smartsource.dell.com/
if you need acrobat xi pro and if you follow all 7 steps you can directly download a trial here: http://prodesigntools.com/adobe-acrobat-xi-pro-standard-reader-direct-download-links.html
and activate with your serial number.
if you have a problem downloading, you didn't follow all 7 steps, or your browser does not accept cookies.
the most common problem is caused by failing to meticulously follow steps 1,2 and/or 3 (which adds a cookie to your system enabling you to download the correct version from adobe.com).
failure to obtain that cookie results in an error page being displayed after clicking a link on prodesigntools.com