If you do not have an Acrobat Reader on your computer, download and save he report files you require, then visit www.adobe.com/products/acrobat  for a free downloadable Reader.
If you have Acrobat, and you know you want to download and save a report, do not attempt to browse the report while downloading. Wait until it is 'done' then click 'save' in the Acrobat toolbar. This is the quickest way to download.
If you have a recent version of Acrobat, and you do not know if you want to save the report, the .pdf files can be downloaded and browsed page at a time.  However,  be aware that after browsing is initiated, pages are only downloaded when prompted by your browsing. When you decide you want to download the report, click 'save' in the Acrobat toolbar and normal, continuous download will be resumed.