Fleettracker also stores uploaded attachments belonging to port calls.
When you are calling the SOAP web services WSAPIImoDcsData.wsdl and WSAPIMrvData.wsdl, you will get a portEmission section:
<imoDcsPortData>
<portEmission xsi:type="ns2:PortEmissionEditDTO">
<ns2:ftId>1234</ns2:ftId>
<ns2:portName>LAS PALMAS</ns2:portName>
<ns2:portCode>ESLPA</ns2:portCode>
<ns2:atd>2022-06-26 22:30:56</ns2:atd>
<ns2:ata>2022-06-26 14:54:00</ns2:ata>
<ns2:countryCode>ES</ns2:countryCode>
...
<ns2:fileReference>
<ns2:url>https://my.fleettracker.de/module/fileReference/downloadFileReference.php?refTable=fahrplan_eintrag&refId=xxx&id=yyy</ns2:url>
<ns2:id>17</ns2:id>
<ns2:fileName>OTTO 2022-06-25 Las Palmas.pdf</ns2:fileName>
<ns2:created>2022-06-27 08:09:07</ns2:created>
</ns2:fileReference>
Under the fileReference section, you find the download URL to retrieve the BDN.
Note: You have to add the credentials companyGuid and clientGuid to the get request.