My suggestion for PDF reader

http://pdfreaders.org

PDF.js - https://github.com/mozilla/pdf.js

https://addons.mozilla.org/En-us/firefox/addon/pdfjs

Because it works with free software browser Firefox.

Regards.

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Minha sugestão para leitor de PDF

http://pdfreaders.org

Sugiro PDF.js https://github.com/mozilla/pdf.js pois funciona com navegador Firefox.

https://addons.mozilla.org/En-us/firefox/addon/pdfjs

Saudações livres.