const { PDFDocument } = require('pdf-lib')
// file = { fileName: 'test1.pdf, content: arraybuffer }
const originalPdf = await PDFDocument.load(file.content, { ignoreEncryption: true })
const newPdf = await PDFDocument.create()
const [firstPage] = await newPdf.copyPages(originalPdf, [0]) // <-- 0 is the first page
newPdf.addPage(firstPage)
const firstPagePdf = await newPdf.save()
file.content = Buffer.from(firstPagePdf)