If you’re looking to check on a system-wide level, then the Server tools that bmike mentioned above might be of more use to you. I don’t have experience with them; I’m recommending two tools that are useful for an individual user.
ClamXav (free, http://www.clamxav.com/) is based on the ClamAV engine that bmike mentioned. It can be told to scan everything on your hard drive, or just files you tell it to (e.g. only files downloaded from the web). Specific to your needs, from their home page: “Clearly lists infected files”. I presume, but am not certain, that such files include PDF and image files.
Virusbarrier ($49.95, www.intego.com/virusbarrier/) and VirusBarrier Plus (99¢, Mac App Store) are both made by Intego. The MAS page claims that this “Finds and repairs Microsoft Word, Excel or PowerPoint documents” and “Finds and eradicates PDF malware”, which seems what you’re looking for. I tried VirusBarrier a couple of years ago, and it seemed pretty decent, but I stopped using it because it was overkill for my purposes.
One of those two might be able to sort you out. Note that they both go after Windows and Mac malware, so you needn’t worry about sending on malware to a Windows PC if you use one of the above (in theory, at least).
If you’re interested, you might also like to look up XProtect. It’s an anti-malware system built into OS X, that looks out for nasty things. It’s not as mature as the two products above (it debuted in mid-2009, IIRC), but it’s a nice tool to have, nonetheless.
As for some of the online services you mentioned, I’ve found various pages from the companies about their policy on scanning email. I’ve never run into any of these antivirus scanners, so I can’t comment on their quality.
Google has an antivirus scanner in Gmail, as explained on this Gmail support page:
Gmail automatically scans every attachment when it's delivered to you, and again each time you open a message. Attachments you send are also scanned. Checking attachments for viruses protects our users and their information, and prevents the spread of viruses.
Similarly, Yahoo! scan and clean all of your attachments:
Yahoo! Mail automatically scans all incoming and outgoing email attachments for known viruses. We use industry-leading Norton AntiVirus software, so you don't have to do a thing. Download the attachment and wait for that reassuring message "No Virus Threat Detected." If a virus is detected, it will be cleaned if possible, and you'll be given further instructions.
I can’t find anything about scanners built into Windows Live Mail, MobileMe or iCloud. That doesn’t mean that they don’t exist; simply that they don’t show up in a Google search.
Hope some of this is useful to you :)