Hi @pandachan48 

To add a new field in Document details, you need to extend the CROpportunityProducts DAC and add this field to cr304000 .aspx page.

I just added a test field and please find the sample example below.

CROpportunityProducts Extended DAC

using PX.Data;
using PX.Data.BQL;
using PX.Objects.CR;

namespace Test
{
    public class CROpportunityProductsExt : PXCacheExtension<CROpportunityProducts>
    {
        #region UsrKNDisplaySKU
         PXDBString(50, InputMask = "")]
         PXUIField(DisplayName = "Test Field")]
        public string UsrTestField { get; set; } 
        public abstract class usrTestField : BqlString.Field<usrTestField> { }
        #endregion
    }
}