First I would recommend you take a look at PageBlaster instead of using Blowery directly. It's a nice product and works well with 3.3x and 4.3x. but if your using the Blowery .dll then add something like this to exclude the .pdf extension.

<blowery.web>   
        <httpCompress preferredAlgorithm="gzip" compressionLevel="high">   
            <excludedMimeTypes>   
                <add type="image/png" />   
                <add type="image/jpeg" />   
                <add type="image/gif" />   
                <add type="application/zip" />   
                <add type="application/x-zip-compressed" />   
                <add type="application/x-gzip-compressed" />   
                <add type="application/x-compressed" />   
                <add type="application/octet-stream" />   
                <add type="application/pdf" />   
            </excludedMimeTypes>   
            <excludedPaths>   
                <add path="Install/" />   
            </excludedPaths>   
        </httpCompress>   
    </blowery.web>

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