In the Add Data widget when I upload a file said that the maximum record limit is 1000, is there a way to upload more than 1000 records?
The 1000 record limit comes from the map or feature service limit set when the publisher publishes the service.
Can the publisher change that limit? How?
Yes. When publishing the service there is a record limit filed that is set to 1000 by default.
Set map service properties—Documentation | ArcGIS Enterprise