If the toolkit Pdftk is available in the system, it will be called to manipulate the PDF files (especially to compress the PDF files).
pdftk(input, operation = NULL, output, other.opts = "compress dont_ask")if ani.options('pdftk') is non-NULL, then this function
returns the status of the operation (0 for success; see
system); otherwise a warning will be issued
the path of the input PDF file(s)
the operation to be done on the input (default to be
NULL)
the path of the output (if missing and input is a
scalar, output will be the same as input)
other options (default to be 'compress dont_ask',
i.e. compress the PDF files and do not ask the user for any input)
Yihui Xie
This is a wrapper to call pdftk. The path of pdftk should
be set via ani.options(pdftk = 'path/to/pdftk').
See the reference for detailed usage of pdftk.
Examples at https://yihui.org/animation/example/pdftk/
pdftk official website https://www.pdflabs.com/tools/pdftk-the-pdf-toolkit/