The link makes use of Javascript:

<a href="#" onclick="javascript: ouverturePopup('Status/DownloadFile.A
+SP?CASNUM=50000&StatusCode=SIARC&DataNo=1'); return false;">50000.pdf
+</a>
[download]

In other words, you should be able to retrieve this particular PDF via the URL:

http://cs3-hq.oecd.org/scripts/hpv/Status/DownloadFile.ASP?CASNUM=5000
+0&StatusCode=SIARC&DataNo=1
[download]

As this doesn't look too complicated to extract, you might get around having to execute the Javascript in this case...