I scanned some old papers into a PDF but the text came out blurry and hard to read, even zoomed in. Is there any way to convert it into a clearer, sharper version?
Honestly, that is annoying, and I have seen it with old scans. Once a page is a blurry image, converting the file cannot add missing detail. The only reliable fix is to rescan the originals at 300 dpi or higher with good light and the document setting in your scanner software. To be fair, raising contrast can help a little, but the text will not become truly sharp.
Do you still have the original papers? If so, rescan them at 300 DPI or higher. Sharpness comes from the scan itself, no converter can add detail back.
If you can’t rescan, run OCR on it with Adobe Acrobat or a free tool and you’ll get clean selectable text, just not the original look.