You can specify a variable that contains an image as a watermark. The following example shows how to create a form from which the user can select an image:

<!--- The following code creates a form where you can choose an image to use 
    as a watermark. --->
<h3>Choosing a Watermark</h3>
<p>Please choose the image you would like to use as a watermark.</p>

<!--- Create the ColdFusion form to select an image. --->
<table>
<cfform action="addWatermark2.cfm" method="post" 
enctype="multipart/form-data">
    <tr>
        <td><img src="../cfdocs/images/artgallery/maxwell01.jpg"/><br/>
        <cfinput type="radio" name="art" value="../cfdocs/images/artgallery/maxwell01.jpg"
            checked="yes">
        Birch Forest</td>
        <td><img src="../cfdocs/images/artgallery/raquel05.jpg"/><br/>
        <cfinput type="radio" name="art" value="../cfdocs/images/artgallery/raquel05.jpg">
            Lounging Woman</td>
        <td><img src="../cfdocs/images/artgallery/jeff01.jpg"/><br/>
        <cfinput type="radio" name="art" 
            value="../cfdocs/images/artgallery/jeff01.jpg">Celebration</td>
        <td><img src="../cfdocs/images/artgallery/paul01.jpg"/><br/>
        <cfinput type="radio" name="art" 
            value="../cfdocs/images/artgallery/paul01.jpg">Guitarist
        </td>
    </tr>
</table>
<br/>
<cfinput type="Submit" name="submit" value="Submit"></p>
</cfform>

The processing page uses the image selected from the form as the watermark for a PDF file:

<!--- ColdFusion applies the image selected from the form as the watermark in a PDF document
    by using the input variable form.art. --->
<cfpdf action="addwatermark" source="check.pdf" image="#form.art#" destination="output.pdf"
    foreground="yes" overwrite="true">
<p>The watermark has been added to your personalized checks.</p>