DrawPixel with smooth edges

I am using DrawPixels on a Texture2D in order to create a painting style application. However, it draws squares which will give a very rough edge. Is it possible to have a more rounded look? Here is my code:

 using UnityEngine;
 using System.Collections;
 
 public class PaintControl : MonoBehaviour 
 {
     public Transform plane;
     public Color color;
     public int Size;
 
     private RaycastHit hit;
     private Color[] paintColors;
 
     // Use this for initialization
     void Start () 
     {
         // init the texture to white
         Texture2D texToWhite = plane.renderer.material.mainTexture as Texture2D;
         Color[] fillColorArray = texToWhite.GetPixels();
 
         for (int i = 0; i < fillColorArray.Length; ++i)
             fillColorArray[i] = Color.white;
 
         texToWhite.SetPixels(fillColorArray);
         texToWhite.Apply();
 
         SetColor(this.color);
     }
 
     // Update is called once per frame
     void Update()
     {
         if (Input.GetMouseButton(0))
         {
             Ray theRay = Camera.main.ScreenPointToRay(Input.mousePosition);
             
             if(Physics.Raycast(theRay, out hit, 50.0f))
             {
                 GameObject go = hit.collider.gameObject;
 
                 if (go.tag == "DrawCanvas")
                 {
                     Debug.Log(Input.mousePosition);
                     Renderer render= hit.collider.renderer;
                     MeshCollider meshColl = hit.collider as MeshCollider;
 
                     Texture2D tex = render.material.mainTexture as Texture2D;
                     Vector2 pixelUV = hit.textureCoord;
 
                     pixelUV.x *= tex.width;
                     pixelUV.y *= tex.height;
 
                     //tex.SetPixel((int)pixelUV.x, (int)pixelUV.y, Color.black);
                     tex.SetPixels((int)pixelUV.x, (int)pixelUV.y, this.Size, this.Size, paintColors);
                     tex.Apply();
                 }
             }
         }
     }
 
     public void SetColor(Color tempColor)
     {
         this.color = tempColor;
         SetSize(this.Size);
     }
 
     public void SetSize(int tempSize)
     {
         this.Size = tempSize;
         paintColors = new Color[tempSize * tempSize];
 
         for (int i = 0; i < paintColors.Length; i++)
             paintColors[i] = this.color;
     }
 }