Create .gitlab-ci.yml in your repository, with the following code.
compile_pdf:
image: aergus/latex
script:
- latexmk -pdf main.tex
artifacts:
paths:
- main.pdf
main.tex is a latex script and main.pdf is its generated pdf document file. Change main in the above code according to your wish.
Find the builds(pdf's) at [https://your-git-domain.com/
Reference: Unknown