Please advise approach to increase Nougat ocr quality for small size super subscript characters

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Attached page PDF normal pdfwithtext.pdf In equation below small superscript letter font-size 5.8 pt tagged x{n}^{(n)} instead of x{u}^{(n)}

[\begin{bmatrix}x{n}^{(n)}\ y{n}^{(n)}\ z{n}^{(n)}\end{bmatrix}=\begin{bmatrix}r{n}^{(n)}s{\theta^{(d)}}c{\phi^{( d)}}\ r{n}^{(n)}s{\theta^{(d)}}s{\phi^{(d)}}\ r{n}^{(n)}c_{\phi^{(d)}}\end{bmatrix},\,n\in{1,\cdots,N}. \tag{3}]

PDF is two column layout academic papers pdfwithtext.pdf with significant number of super, subscripts, some as small as 4.2 pt Please advise approach to increase ocr quality for these small size super subscript characters Normal size characters ocr is good. Thank you