The reader in which one can read the pdf is fine, but it does not follow links (say a link like [8] to the literature), while the desktop version does.
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The reader does follow intra-PDF links, and it then includes a back button to go back to the previous page. If you're not seeing that somewhere, the citations may not be active links in the PDF.
If you're not seeing it anywhere, provide a link to a PDF as well as a screenshot of what you're tapping.
Indeed, mostly it works, apparently I maybe encountered only one example where the Android version does not follow links while the desktop version does: https://ieeexplore.ieee.org/document/4389510, 10.1109/FOCS.2007.18
Those aren't actually links in the PDF. The Zotero Desktop reader has dedicated logic to detect citations and link them to the bibliography which the Android readers doesn't have, but the links here are not in the PDF itself (you can try opening it with any other PDF reader)
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The reader does follow intra-PDF links, and it then includes a back button to go back to the previous page. If you're not seeing that somewhere, the citations may not be active links in the PDF.
If you're not seeing it anywhere, provide a link to a PDF as well as a screenshot of what you're tapping.
https://ieeexplore.ieee.org/document/4389510,
10.1109/FOCS.2007.18