I have my tax return saved as a PDF and need to fix a couple entries before the deadline this week but can’t edit it on my laptop without issues.
Honestly the easiest fix is going back to whatever you used to prepare it and correcting the entries there, then saving a fresh PDF. Most tax software lets you reopen your return. If it’s a fillable IRS form, open it in your browser and the boxes should still be editable.
I had this exact trouble fixing our clinic tax forms last year. What worked for me was uploading it to PDFcap, using the text edit tool to amend the numbers, and saving a new copy. It kept all the formatting intact without freezing my old computer, so it might be worth a try before your deadline.