On Android, there's e.g. Moon+ Reader Pro supporting PDF and text-to-speak:
Moon+ Reader Pro: Read aloud, ColorDict, Highlight/Annotate (Source: Google Play; click images for larget variants)
As the screenshots show, it's pretty configurable: not only can you adjust volume, but also speed. A bunch of additional features make it very much fit for your purpose: you can highlight/annotate text (for study material, this is probably a must). With PDF files, these annotations/highlights are directly stored into the
.pdf file and additionally in "Moonies" database for faster access (with other formats, it's only stored in the database) – so you can later process your annotations/highlights on a different computer. Furthermore, it supports different dictionaries like Fora or (my recommendation) ColorDict – both capable of online and offline dictionaries and using standard formats (ColorDict even offers to install some of them from within the app, while for Fora you'd need to do that manually).
For Text-to-Speech, Moon+ relies on the TTS engine provided by the system. Depending on the language used (and the quality of speech support for it), quality varies; for English it seems to be pretty good, for German I wouldn't use it to read me a novel (but that's a general thing: TTS cannot detect "moods" of the text it reads). Words are pronounced accurately.
Though not specifically tailored to academic text, I think it's a good match (especially considering you might want to use it "on the road", where a tablet/smartphone is preferable to a laptop) – and currently offered for 50% off at Google Play. I'm a long-time user of Moon+ and really love it. Support is great, and the app very reliable.
There's a free (ad supported) version available for a first look, but that doesn't support PDF nor TTS, unfortunately.
PS: As an afterthought. I rarely use PDF (mostly only to proof-read print variants of my books sent to me by my publisher), and almost never TTS – so I cannot say how well these two features work together (though the app description explicitely states: PDF support, fast & speech compatible, so it should work or Seany wouldn't state so). Furthermore, I doubt it will work with e.g. PDFs only composed of images, as Moon+ to my knowledge doesn't contain an OCR engine to extract text from images.