A number of Online AV Multiscanner services allow users to check individual files to see if they are malicious.
The following services can be used to upload and scan suspicious files and URLs with multiple scan engines and/or blacklists.
There are more such sites, but we regard the few above ones as the most relevant and legal ones.
Please always keep in mind that such sites use different products (i.e. command line scanners) with different settings than the actual/real products, beside only telling whether a file is detected during a static on-demand scan.
Important: never submit/upload personal documents or sensitive data to such services, as submitted files get shared among several companies and individuals that subscribed to get feeds and metadata from uploaded files.