MacOS – Mavericks: Safari does not recognize PDFs and shows them inline

Since upgrading to Mavericks Safari does not recognize PDFs anymore and shows them inline (as text)

%PDF-1.3 %âãÏÓ %RSTXPDF3 Parameters: D 2 0 obj << /Filter 3 0 R /Length 4 0 R /Length1 772192
>> stream xœì½Ü¥Ey6>眧÷rÚÛvØ]úÂB`³j])†"ŠØ5¶(Š ¶Ä***Á5vb"1ˆb׈
%v’hì=ÿëºgæœçœ·ìBòñýòý3Ï{ÏóIOØðÆůܢZŸú©RÞýÏyÌÃÎÿôSp™j}èZ\?êa}ücÔP…
[...]

Before upgrading the very same files from the same sites where downloaded as PDFs and shown with Preview (the are delivered with the correct MIME type).

I do not have any Adobe Reader plugin (checked both /Library/Internet Plugins and ~/Library/Internet Plugins.

Open "safe" files after downloading is checked in Safari's options.

Any idea on what could be wrong and how to fix it?

Edit

This is only happening on one machine (I tested the same URLs with other Mavericks installations and they are displayed correctly).

The MIME type handling seems OK. defaults read /Applications/Safari.app/Contents/Info.plist gives:

    {
        CFBundleTypeExtensions =             (
            pdf
        );
        CFBundleTypeIconFile = "document.icns";
        CFBundleTypeMIMETypes =             (
            "application/pdf"
        );
        CFBundleTypeName = "PDF document";
        CFBundleTypeRole = Viewer;
        NSDocumentClass = BrowserDocument;
    },

On both machines