我有一个pdf文件，我想从中提取文本。但由于缺少toUniCode地图，我无法做到。
./pdffonts /Users/subhashlengare/Downloads/pqr39_abc.pdf
name type emb sub uni object ID
------------------------------------ ----------------- --- --- --- ---------
ATRTHG+TT1CABt00 TrueType yes yes no 23 0
VFQVYH+TT1CAEt00 TrueType yes yes no 19 0
ODNMDG+TT1CAFt00 TrueType yes yes no 31 0
DXGYRQ+TT1CB0t00 TrueType yes yes no 27 0
VFQVYH+TT1CB1t00 TrueType yes yes no 7 0
ArialMT TrueType no no no 295 0
NXBBUP+TT1CC0t00 TrueType yes yes no 53 0
NXBBUP+TT1CC1t00 TrueType yes yes no 65 0
KDGXKF+TT1CC4t00 TrueType yes yes no 104 0
VRCBAT+TT1CC5t00 TrueType yes yes no 100 0
QTNBCJ+TT1CC2t00 TrueType yes yes no 88 0
NXBBUP+TT1CC6t00 TrueType yes yes no 96 0
NXBBUP+TT1CC7t00 TrueType yes yes no 116 0
NXBBUP+TT1CC8t00 TrueType yes yes no 128 0
我们如何添加缺少的ToUniCode映射，以便文本提取效果良好？