Thank you for sharing your question with our network. Sometimes when you have a large order, packing slips will inevitably move to the second page to accommodate for the extra space it takes up.
As a workaround, you can head to Settings > Shipping & Delivery > edit Packing slip template and play around with the margins if it's only over by one or two lines frequently. An alternative recommendation is to move to a 4x6 packing slip template, for which we have an incredibly detailed tutorial.
If I missed or misunderstood anything please let me know.
Olivia | Social Care @ Shopify - Was my reply helpful? Click Like to let me know! - Was your question answered? Mark it as an Accepted Solution - To learn more visit the Shopify Help Center or the Shopify Blog