% Characters the T1 text font lacks, set with the glyphs the sealed build took from TeX Gyre Pagella Math.
\usepackage{newunicodechar}
% Greek letters and symbols in running text come, as in the sealed build, from the TeX Gyre Pagella text fonts
% themselves (the same Type 1 fonts through their QX, OT1 and TS1 encodings); in mathematics, newpxmath.
\DeclareFontEncoding{QX}{}{}
\DeclareFontSubstitution{QX}{qpl}{m}{n}
\newcommand\rsqx[1]{{\fontencoding{QX}\selectfont\symbol{#1}}}
\newcommand\rsotone[1]{{\fontencoding{OT1}\selectfont\symbol{#1}}}
% The text layer as in the sealed PDF: ToUnicode from the glyph names (the font's Delta is the Greek capital, U+0394, as in its OpenType cmap).
\ifdefined\pdfgentounicode\input{glyphtounicode}\pdfglyphtounicode{Delta}{0394}\pdfgentounicode=1\fi
\newunicodechar{²}{\texttwosuperior}
\newunicodechar{¹}{\textonesuperior}
\newunicodechar{Γ}{\ifmmode\Gamma \else\rsotone{0}\fi}
\newunicodechar{Δ}{\ifmmode\Delta \else\rsqx{1}\fi}
\newunicodechar{Φ}{\ifmmode\Phi \else\rsotone{8}\fi}
\newunicodechar{β}{\ifmmode\beta \else\rsqx{2}\fi}
\newunicodechar{δ}{\ifmmode\delta \else\rsqx{3}\fi}
\newunicodechar{′}{\ifmmode^{\prime}\else\ensuremath{^{\prime}}\kern0.0172em\relax\fi}
\newunicodechar{ℝ}{\ensuremath{\mathbb{R}}}
\newunicodechar{ℤ}{\ensuremath{\mathbb{Z}}}
\newunicodechar{→}{\ifmmode\rightarrow\else\textrightarrow\fi}
\newunicodechar{∂}{\ifmmode\partial\else\ensuremath{\uppartial}\kern0.03em\relax\fi}
\newunicodechar{∞}{\ifmmode\infty \else\rsqx{173}\fi}
\newunicodechar{≥}{\ifmmode\geq \else\rsqx{132}\fi}
\newunicodechar{𝑂}{\ensuremath{O}}
\newunicodechar{𝑠}{\ensuremath{s}}
\newunicodechar{𝑡}{\ensuremath{t}}
\newunicodechar{𝛿}{\ensuremath{\delta}}
\newunicodechar{𝜁}{\ensuremath{\zeta}}
\newunicodechar{𝜑}{\ensuremath{\varphi}}
% Figures in the small-caps field labels (\RSfield, rs-header.tex): the T1 TeX Gyre Pagella small-caps fonts
% carry old-style figures, the sealed build's small caps (OpenType smcp) the lining ones; set them in the upright shape (a plain shape switch: \textup would add an italic correction).
\ExplSyntaxOn
\tl_new:N \l__rs_label_tl
\cs_new_protected:Npn \__rs_lining:n #1
  {
    \tl_set:Nn \l__rs_label_tl {#1}
    \regex_replace_all:nnN { ([0-9]+) } { \cB\{ \c{fontshape} \cB\{ n \cE\} \c{selectfont} \1 \cE\} } \l__rs_label_tl
    \tl_use:N \l__rs_label_tl
  }
\AtBeginDocument
  {
    \cs_if_exist:NT \RSfield
      {
        \cs_set_eq:NN \__rs_field_sealed:n \RSfield
        \cs_set_protected:Npn \RSfield #1 { \__rs_field_sealed:n { \__rs_lining:n {#1} } }
      }
  }
\ExplSyntaxOff