If you recovered some valid jpg and pdf files without filenames, you might be able to identify them to some extent.
For PDFs that contain text (not just scans), you can get back some of the text with:
$ pdftotext /home/paul/Downloads/Canalside/CAR*.pdf - > SomePDF.txt
$ wc SomePDF.txt
85 406 2535 SomePDF.txt
$ head -n 4 SomePDF.txt
If they have some consistent format, you could parse the text for titles or page footers. You might even find an OCR option for scanned images.
For .jpg files, the
file command outputs a
datetime value, which is at least a unique name, and gives you a sequence and a possible identity (maybe you keep a calendar or time-sheets to correlate against).
$ file /media/paul/Windows/30_Photos/PhotoStore/A810_Folders/119_1402/IMG_1280.JPG
/media/paul/Windows/30_Photos/PhotoStore/A810_Folders/119_1402/IMG_1280.JPG: JPEG image data, Exif standard: [TIFF image data, little-endian, direntries=10, description= , manufacturer=Canon, model=Canon PowerShot A810, orientation=upper-left, xresolution=194, yresolution=202, resolutionunit=2, datetime=2013:02:14 10:49:18], baseline, precision 8, 4608x3456, frames 3