How to build a personal PDF link for a Mailchimp merge field

Task

Each contact needs PDF_URL like https://site.example/files/{customer_id}.pdf. If customer_id is empty, no link should be exported.

Short answer

Create PDF_URL from customer_id, add the prefix and .pdf only for non-empty values, then require a non-empty result.

How to do it in Eofferix

Upload the contacts table and open the table editor.
The preview shows only rows with non-empty customer_id and a ready personal link.
Create PDF_URL from customer_id: replace empty values with empty output; for non-empty values add https://site.example/files/ and .pdf.
Prefix and suffix are added only when customer_id is not empty.
Add a result condition: export the field only when PDF_URL is not empty.
Save the template and use the column as a Mailchimp merge field.

The data below is a training example and does not belong to real user files.

source data

result

contact_id	PDF_URL
C-1001	https://site.example/files/1024.pdf
C-1003	https://site.example/files/2048.pdf