namespace error

We have fixed the bug, but providing a new bug-fixed package will take some time because of Unity’s asset publishing policies and procedures.

As a quick fix, could you please do the following:

1. Open the file ‘Assets/Editor Default Resources/xDoc-FreeReader/Scripts/Annotation.cs’ in any text editor.
2. Replace all content with the code provided at the end of this answer.
3. Please feedback, if it fixed your problem or not.

// File: Annotation

namespace xDoc
{

#if UNITY_EDITOR

    using UnityEngine;
    using xDocBase;

    [HelpURL ("http://xoxinteractive.com/questions/category/xdoc/")]
    [AddComponentMenu (Annotation.menuPath, Annotation.menuPosition)]
    public class Annotation : XDocAnnotationBase
    {
        public const int menuPosition = -999;
        public const string menuPath = "xDoc Annotation";
    }

#else
    
    using UnityEngine;

    public class Annotation : MonoBehaviour
    {
        /// <summary>
        /// This function is called when the object becomes enabled and active.
        /// As result the annotation is deleted from the gameObject.
        /// -> Only for built applications / programs, when the annotation
        /// is not needed anymore.
        /// </summary>
        private void OnEnable()
        {
            Destroy(this);
        }
    }

#endif
}