It may be that your are viewing the documents in an application other than Adobe Acrobat Reader. To view the posters properly you need to have a copy of Adobe Acrobat Reader installed on your computer and set as your default PDF viewing application. To ensure you have the latest version of Acrobat installed, please visit the following web address https://get.adobe.com/uk/reader/
If this does not work and you are sure that you have Acrobat Reader installed, download the poster to your desktop and right click the icon and open with Acrobat.