Thanks for using the MyWoodlot forum and congratulations on your property purchase. I did a Google search for "app to find property lines" and came up with a few results that might be helpful.
Landglide (for Apple products): LandGlide is the most comprehensive parcel data mobile app. Using GPS technology to pinpoint your exact location, you can explore maps and access 150 million parcel records in over 3,000 counties - covering more than 95% of the U.S. population. https://apps.apple.com/us/app/landglide/id560902465
onX Hunt: Lets you navigate property lines with confidence by always knowing where you stand with GPS tracking and clearly-marked boundaries. Our proprietary data collection, analysis and layering methods handled by our Geographic Information System (GIS) team gives you the most accurate and up-to-date maps available on all devices—all in one place. Available for iOS, Android and Web. https://www.onxmaps.com/hunt/app/features/property-lines
Note that Landglide and onX come with property boundary information, but will require you to pay for a subscription, unless you can do what you need to do within the free trial period.
Another option is Avenza. They offer a free version that allows you to use up to 3 .pdf maps at a time: https://www.avenzamaps.com/maps/version-comparison.html. However, Avenza doesn't come with maps that show property boundaries, or any other maps for that matter. You'd have to create a .pdf map showing your property boundaries elsewhere, save it, and upload it to Avenza.
If your property is located in the New York City Watershed (find out here: https://www.mywoodlot.com/mywoodlot-mapping-tool) and you want help to make a property map that shows your boundaries, send me an email at email@example.com and I will put you in contact with one of our Watershed foresters. They have access to ArcGIS and could make a map for you. This would be a way to get a map of your property boundaries that you could use on your smartphone for free. That is, you download the free version of Avenza and we'd send you a .pdf map of your property to use in Avenza.