Once the image exists, it has to get onto the document. Each program handles it a little differently.
Word and Hangul
Insert → Picture, then set the wrapping to in front of text. That is what lets you drag the seal onto the signature line. Because the background is transparent, the lines and text underneath show through.
Editing a PDF directly needs paid software. It is usually simpler to place the seal in the source document and export to PDF from there.
E-contract services
Most e-contract platforms offer a «upload seal image» field and ask for a transparent PNG — exactly what BaroStamp produces. If there is a file-size limit, re-export at 150 dpi.
One limit to remember
An image seal does not replace a physical registered seal or its certificate. Transactions that require a seal certificate — property registration, inheritance, mortgages — need the registered physical seal. Image seals belong on internal approvals, quotations, delivery notes and agreed e-contracts, where both parties can already identify each other.