This site is SAFE.
I ran the same Site-Scans as @Hotdoge3 did (on 07/27/2015) and both scans now show SumatraPDFReader.org as SAFE.
1) FREE Online Website Malware Scanner | Website Security Monitoring & Malware Removal | Quttera: http://quttera.com/detailed_report/sumatrapdfreader.org
2) Sucuri SiteCheck - Free Website Malware Scanner https://sitecheck.sucuri.net/results/sumatrapdfreader.org
http://quttera.com/detailed_report/sumatrapdfreader.org
Severity: Suspicious
Reason:
Detected reference to blacklisted domain.william,famille-blum,0rg
Don't click that link
Server IP address: 162.243.137.163
Country: United States
Server: nginx/1.4.1
Malicious files: 0
Suspicious files: 1
Potentially Suspicious files: 0
http://www.urlvoid.com/scan/sumatrapdfreader.org/
Safety Reputation 0/29
Domain 1st Registered 2013-10-23 (2 years ago)
Server Location Flag (US) United States
https://sitecheck.sucuri.net/results/sumatrapdfreader.org
ISSUE DETECTED DEFINITION VULNERABLE HEADER
Outdated Web Server Nginx Found Vulnerabilities on nginx nginx/1.4.1
Installer: SumatraPDF-3.0-install.exe very good & fast
Portable version: SumatraPDF-3.0.zip very good