Which of the following is a significant change a Purchase Requisition Processor can make on an existing PR?

A significant change a Purchase Requisition Processor can make on an existing Purchase Requisition (PR) is adding a line item to purchase additional goods. This action is crucial as it directly impacts the scope of the requisition. When an additional line item is added, it represents a request for more materials or services that were not previously included in the initial PR. This reflects the dynamic nature of procurement needs and allows for adjustments to be made in response to changing requirements within an organization.

In the context of the other options, while they may involve modifications to the PR, they don’t have the same level of impact on the overall intent of the requisition. Changing a vendor's contact information, for example, is an administrative change that doesn’t affect the quantity or nature of what is being requested, nor does deleting the entire PR or just modifying the delivery date substantially alter the goods or services being procured. Therefore, adding a line item stands out as a significant modification that genuinely broadens the procurement request and aligns it with operational needs.