There isn't any build-in functionality for reading PDF files in PowerShell so your best bet is to use a third party .NET component. There are several commercial and also at least a few free open source alternatives.
Here's a few lines of example code using iTextSharp to read the PDF:
Add-Type -Path .\itextsharp.dll
$pdfReader = New-Object iTextSharp.text.pdf.PdfReader("C:\file.pdf")
$textFromFirstPage = [iTextSharp.text.pdf.parser.PdfTextExtractor]::GetTextFromPage($pdfReader, 1)
$pdfReader.Dispose()
How you go about finding your account id after that of course depends on the text of your files.