We've built a force.com site and we have the A5 Apps package installed to generate a PDF. Upon completion of a transaction, we want to download the pdf. However I'm getting error messages saying the URL is down or incorrect. 

Below is a sample of the code and was wondering whether some can assist with what the correct URL is?
 

<div class="section section--success" data-accordion="section-4-success" id="section-4-success">
        <div class="section__inner success">
            <div class="section-title section-title--success">YOU’RE COVERED FOR ANOTHER YEAR</div>
            <p class="success__focus">THANK YOU FOR RENEWING YOUR KIA EXCESS RETURN POLICY</p>
            <p class="section-title-success-text">We’ve emailed your certificate of cover. Keep it somewhere safe.</p>
            <div class="success__download">
                <span id="generating" class="btn btn--generating">Please Wait...</span>
                <button class="btn btn--next btn--download-certificate" id="downloadBtn" onclick=" downloadLink()"  href="/servlet/servlet.FileDownload?file=" >
                    <svg xmlns="http://www.w3.org/2000/svg" x="0px" y="0px"
                         width="25" height="25"
                         viewBox="0 0 224 224"
                         style=" fill:#000000;">
                        <g fill="none" fill-rule="nonzero" stroke="none" stroke-width="1" stroke-linecap="butt"
                           stroke-linejoin="miter" stroke-miterlimit="10" stroke-dasharray="" stroke-dashoffset="0"
                           font-family="none" font-weight="none" font-size="none" text-anchor="none"
                           style="mix-blend-mode: normal">
                            <path d="M0,224v-224h224v224z" fill="none"/>
                            <g fill="#cd0025">
                                <g id="surface1">
                                    <path d="M111.02,13.16c-4.62,0.5075 -8.085,4.4625 -7.98,9.1v106.26l-16.1,-16.1c-1.89,-1.9425 -4.5675,-2.9225 -7.28,-2.66c-3.4825,0.3325 -6.4575,2.6775 -7.595,5.985c-1.155,3.325 -0.2625,7 2.275,9.415l37.66,37.66l37.66,-37.66c2.345,-2.24 3.3075,-5.565 2.5025,-8.715c-0.805,-3.1325 -3.2375,-5.6 -6.37,-6.44c-3.1325,-0.84 -6.475,0.0875 -8.7325,2.415l-16.1,16.1v-106.26c0.035,-2.4325 -0.91,-4.76 -2.625,-6.475c-1.715,-1.715 -4.0425,-2.66 -6.475,-2.625c-0.28,-0.0175 -0.56,-0.0175 -0.84,0zM8.96,161.28v25.48c0,6.615 2.0125,13.02 6.72,17.5c4.7075,4.48 11.1825,6.3 17.64,6.3h157.5c6.545,0 13.02,-1.855 17.64,-6.44c4.62,-4.585 6.58,-11.2175 6.58,-17.78v-25.06h-17.92v25.06c0,3.29 -0.7,4.4975 -1.26,5.04c-0.56,0.5425 -1.7325,1.26 -5.04,1.26h-157.5c-3.395,0 -4.6375,-0.7525 -5.18,-1.26c-0.5425,-0.5075 -1.26,-1.365 -1.26,-4.62v-25.48z"/>
                                </g>
                            </g>
                        </g>
                    </svg>
                    <p style="float: right; margin-left: 10px;">DOWNLOAD YOUR CERTIFICATE</p>
                </button>
            </div>