convert data: Array to ArrayBuffer

I need to convert a PDF data array type buffer into an ArrayBuffer. here's an example

this.templateService.get(data[0].templateId).subscribe({
          next: async (data) => {
            this.datatemplate = data.datatemplate  


this.datatemplate {type: 'Buffer', data: Array(185251)} // type of data

when i try to read this data using PDF-LIB,

const pdfDoc = await PDFDocument.load(this.datatemplate)
    const form = pdfDoc.getForm()
    const fields = form.getFields()
    fields.forEach(field => {
      const type = field.constructor.name
      const name = field.getName()
      console.log(`${type}: ${name}`)
    })

I've got this error

TypeError: pdf must be of type string or Uint8Array or ArrayBuffer, but was actually of type NaN

any help please?