Extracting data from multiple pdf files in R - r

Question

Below is the code to create some test data:
df <- data.frame(page_id = c(3,3,3,3,3), element_id = c(19, 22, 26, 31, 31),
text = c("The Protected Percentage of your property value thats has been chosen is 0%",
"The Arrangement Fee payable at complettion: £50.00",
"Interest rate is fixed for the life of the period is: 5.40%",
"The Benchmark rate that will be used to calculate any early repayment 2.08%",
"The property value used in this scenario is 275,000.00"))
I have many pdf files from which I want to extract the same information using regular expressions. I have managed to extract all the information I require from 1 pdf file so far. Below is the code for it - with comments:
library("textreadr")
library("pdftools")
library("tidyverse")
library("tidytext")
library("textreadr")
library("tm")
# read in the PDF file
Off_let_data <- read_pdf("50045400_K021_2017-V001_300547.pdf")
# read all pdf file from a folder
files <- list.files(pattern = "pdf$")[1]
# extract the account number from the first pdf file
acc_num <- str_extract(files, "^\\d+")
# The RegEx's used to extract the relevant information
protec_per_reg <- "Protected\\sP\\w+\\sof"
Arr_Fee_reg <- "^The\\sArrangement\\sF\\w+"
Fix_inter_reg <- "Fixed\\sI\\w+\\sR\\w+"
Bench_rate_reg <- "Benchmark\\sR\\w+\\sthat"
# create a df that only includes the rows which match the above RegEx
Off_let <- Off_let_data %>% filter(page_id == 3, str_detect(Off_let_data$text, protec_per_reg)|
str_detect(Off_let_data$text, Arr_Fee_reg) | str_detect(Off_let_data$text, Fix_inter_reg) |
str_detect(Off_let_data$text, Bench_rate_reg))
# Now only extract the numbers from the above DF
off_let_num <- str_extract(Off_let$text, "\\d+\\.?\\d+")
# The first element is always a NA value - based on the structure of these PDF files
# replace the first element of this character vector with the below
off_let_num[is.na(off_let_num)] <- str_extract(Off_let$text, "\\d+%")[[1]]
off_let_num
The off_let_num variable is a vector with has 4 elements that are required from the pdf file.
NOW I would like to apply all these steps to a folder that includes many pdf file. So, far I have managed to read all the PDF file into separate data frames - the code for which is below:
# read all pdf files into a list
file_list <- list.files(pattern = '*.pdf')
# Read in all the pdf files into seperate data frames
for (file_name in off_let) {
assign(paste0("off","_",sub(".pdf","",file_name)), read_pdf(file_name))
}
I now have a many data frames in my working directory. I would like to apply the same process I applied to one pdf file in the start, to all these data frames beginning with 'off'.
I guess the way to go would be to convert the initial process into a function and then call this function to be applied to all the data frames beginning with 'off'. The results should be appended to a data frame which should include all the elements (4) extracted from these pdf files.
I'm not sure how to achieve this. Please help!