[R] Warning object has offset 0. PDF file

[Jean-Louis Abitbol]

Good day to all

Using 
> library(pdftools)
Using poppler version 23.04.0

I get a number of warnings such as:

> pdf_subset(infile, pages = 156:157, output = outfile)
WARNING: /Users/jla/Library/CloudStorage/Dropbox/7cordas/Caio/record/90 NEW RODA SONG BOOK.pdf (object 7 0): object has offset 0
WARNING: /Users/jla/Library/CloudStorage/Dropbox/7cordas/Caio/record/90 NEW RODA SONG BOOK.pdf (object 175 0): object has offset 0
WARNING: /Users/jla/Library/CloudStorage/Dropbox/7cordas/Caio/record/90 NEW RODA SONG BOOK.pdf (object 254 0): object has offset 0

This does not prevent from getting the pages extracted properly and written to a pdf file which is readable. Aging is probably the cause of my irritation with such warnings.

 I assume there is a problem with the source pdf file which was assembled by music amateurs using various sources.

My question maybe out of the scope of this list is:

How can I detect and potentially correct using appropriate open source software what is wrong with the pdf file. 
I am on macos.

Thanks for any pointers and best wishes, Jean-Louis