**For a keepsake, your best inexpensive option is to remove the fruit and dry the signed peel.** There’s no reliable home method that will keep a whole orange looking fresh indefinitely.

Photograph every signature clearly before doing anything, then:

1. **Carefully remove the peel in large sections**, cutting between signatures. Remove the flesh and loose pulp from the inside; avoid rubbing or wetting the ink.
2. **Dry the peel with gentle heat and airflow**, preferably in a borrowed food dehydrator. Citrus peel dries well, although drying times depend on thickness and equipment. Expect some shrinking, curling and darkening, which may distort the signatures. [University of California guidance](https://ucanr.edu/site/uc-master-food-preserver-program-orange-county/oranges)
3. **Once thoroughly dry and cool, store it in an airtight container**, with a silica-gel packet kept separate from the peel. Watch for condensation; if any appears, it needs further drying. Keep it somewhere cool and dark—felt-tip inks can fade with light exposure. [Canadian Conservation Institute](https://www.canada.ca/en/conservation-institute/services/care-objects/paper-books/basic-care-art-paper.html)

That’s an adaptation of food-drying methods, rather than a proven autograph-conservation technique, so **try it on another orange marked with the same pen first**, if possible. Avoid applying varnish or resin without testing: compatibility with the ink is uncertain.

Refrigeration only buys time—fresh oranges typically last weeks refrigerated. Freezing would require continued frozen storage and wouldn’t give you a lasting room-temperature display. Within your $40 budget, I’d prioritize a container and desiccant, and borrow a dehydrator. The photographs remain your most dependable backup.

I don’t see the edited picture attached here, so I can’t suggest where best to cut around the signatures.