How to resolve the error of processing multiple pdf files in R script

library(readtext)
data_dir <- system.file("E:/project_refrences", package = "readtext")
rt7 <- readtext(paste0(data_dir, "*.pdf"), docvarsfrom = "filenames", 
                 docvarnames = c("document", "language"))

I tried and getting this Error while processing multiple pdf files:

## PDF error: xref num 65 not found but needed, try to reconstruct<0a>
## PDF error: Invalid Font Weight
## PDF error: Invalid Font Weight
## PDF error: Invalid Font Weight
## PDF error: Invalid Font Weight
## PDF error: Invalid Font Weight

I also tried by applying for loop:

pdf <- Sys.glob("*.pdf")
for(i in pdf){
    rt <- readtext((i), docvarfrom = "filenames", docvarnames = c("document", "language"))}

but getting same above mentioned error.
How can I fix this error or work around it?