Distance between floats on the top or the bottom and the text.
Default value (article class): 20.0pt plus 2.0pt minus 4.0pt
Distance between two floats.
Default value (article class): 12.0pt plus 2.0pt minus 2.0pt
Distance between floats inserted inside the page text and the text proper.
Default value (article class): 12.0pt plus 2.0pt minus 2.0pt
Distance between a float spannign both columns and text.
Default value: 20.0pt plus 2.0pt minus 4.0pt
Distance between two floats spanning both columns.
Default value: 12.0pt plus 2.0pt minus 2.0pt
Amount of space to place above a display equation.
Default value: 0.0pt plus 3.0pt
Amount of space to place below a display equation.
Default value: 6.0pt plus 3.0pt minus 3.0pt
Amount of space to place above a display equation.
Default value: 10.0pt plus 2.0pt minus 5.0pt
Amount of space to place below a display equation.
Default value: 10.0pt plus 2.0pt minus 5.0pt
Amount of space between paragraphs
Paragraph indentation.
Inter-line spacing.
Default: \linespread{1.0}
Include paralist package
Replace \begin{itemize} with \begin{compactitem}
Replace \begin{enumerate} with \begin{compactenum}
Include titlesec package
To change spacings:
\titlespacing{\section}{0pt}{2ex}{1ex}
\titlespacing{\subsection}{0pt}{1ex}{0ex}
\titlespacing{\subsubsection}{0pt}{0.5ex}{0ex}
Docs: http://tug.ctan.org/tex-archive/macros/latex/contrib/titlesec/titlesec.pdf
https://robjhyndman.com/hyndsight/squeezing-space-with-latex/
https://tex.stackexchange.com/questions/387572/techniques-to-reduce-the-number-of-pages-in-a-compiled-pdf
https://www.silverf0x00.com/shrinking-a-latex-paper-to-fit-under-the-page-limits/