library(fulltext)

# Search
## Seaerch for arXiv papers
res <- ft_search(query='ecology', from='arxiv')

## Get arXiv ids
ids <- res$arxiv$data$id

## Fetch PDFs
out <- ft_get(ids, from = "arxiv", cache=TRUE, backend="rds", path = "mypdfs")

## see your folder mypdfs (should be pdfs in there)

## paths to pdf files
out$arxiv$data$path

## path to a single file
out$arxiv$data$path$`hep-ph/9303206v1`

# Extract text
## extract all text
texts <- ft_extract(out)

## text from a single article
texts$arxiv$data$data[[1]]

## Or, you can do it manually
pdftools::pdf_text(out$arxiv$data$path$`hep-ph/9303206v1`)