There is an issue with the Adobe Reader (and Acrobat) 9.0 PDF Link Helper ActiveX control for Internet Explorer (6 or 7) on Windows computers with respect to proxy servers. Due to this issue, there is a 2 minute delay for any Internet Explorer web browser on the Deere network before any PDF file will open from the Internet within the IE web browser if In-Place activation (Display PDF in Browser) is enabled in Adobe Reader 9. This problem does not affect Adobe Reader 8.
What we are seeing is that when someone on the Deere network clicks on a links to a PDF file in the Internet, the PDF file downloads immediately. But then, after the PDF file is downloaded, the Adobe Reader 9 PDF Link Helper ActiveX control tries to talk directly to the Internet web site. The Adobe Reader 9 PDF Link Helper ActiveX control does not know how to negotiate our proxy server. So after a minute or two, the Adobe Reader 9 PDF Link Helper ActiveX control times out (gives up) and allows the IE browser to display the downloaded PDF file in the IE browser.
We work around this issue by disabling In Place Activation for PDF files in IE (uncheck Display PDF in Browser). But we would like a fix for the PDF Link Helper ActiveX control.
Here's what our proxy people see when they do a trace of a PDF file download through their proxy server with IE 7 and Adobe Reader 9 with Display PDF in Browser checked.
The browser tells the proxy to download the pdf, it does and sends it to the browser. Before the browser opens it something in Acrobat ( or I.E. ? ) tries to make a connection back to the content server that hosted the pdf. Unfortunately this agent does not ask the proxy to make the request for it, but rather asks local DNS to resolve the Internet server name. This request dies because our internal private network does not know anything about the Internet. Only the DNS used by the proxy can resolve Interent names. After two unsuccessful DNS queries into the private network, the agent tries to resolve the same Internet name with NBNS ( netbios name service) queries again into the private network, with the same results. These requests persists for more than two minutes ( over 200 unresolved queries ). Then for whatever reason the agent gives up and the already downloaded pdf file loads into the browser.