Most people choose Adobe Reader by default, but there are alternatives.

Hanover, Germany - PDF viewers are standard issue for any computer that needs to post documents online or read such forms.

Most people choose Adobe Reader by default, but there are alternatives.

What's key is making sure you find the one right for you. The selection ranges from separate programmes to applications integrated into operating systems.

Many are free. It's not the worst idea to install two, since every reader comes with its weaknesses.

Worse, according to a test by German computer magazine c't, although many are of high quality, they are not forthcoming about the kind of documents they can't support, whether those be 3D objects, spreadsheets or commentaries. Thus, the second reader becomes a backup.

Most of the preinstalled readers that come with Windows 8, OS X, Chrome and Firefox are perfectly adequate for most documents.

But a backup viewer can come in handy when there are forms that must be filled in, for example. These backups are usually free, although fee-based extensions are sometimes necessary to access additional features.

Annoyingly, the need for those extensions is sometimes only made clear after users attempt to access specific functions.

What is clear is that anyone who wants to digitally sign PDF documents will have to pay for the service, which is not available on any of the free software. Be sure to regularly update your viewer.

PDF documents are a favourite vehicle for hackers trying to get malware onto the computer of unsuspecting people.

The more popular a reader, the more likely that attacks have been created for it. In fact, it can sometimes be a good idea to run extensions for PDF readers in secure mode, blocking them from running Javascript.

That makes it harder for attackers, but can also lead to problems with PDFs that have fields to be filled in or that contain multimedia elements. - Sapa-dpa