YACReader for macOS uses a precompiled single static library version of pdfium.

pdfium branch used for building: chromium/3729

build parameters used (gn args):

pdf_enable_xfa = false
pdf_enable_v8 = false
pdf_is_complete_lib = true
is_official_build = true
use_jumbo_build = true
is_debug = false
symbol_level = 0
 
Instructions on building pdfium can be found at https://pdfium.googlesource.com/pdfium

It is recommended to always use the branch the current stable version of Chromium uses.
To get the pdfium branch corresponding to Chromium stable, look at 
http://omahaproxy.appspot.com and search for the true_branch variable associated with
the current stable dev channel of Chromium.