How to change the numbers on a PDF invoice or order and keep the totals right
blupdf Team · 2026-09-08 · 5 min read
The invoice went out with the wrong quantity on line three. The quote needs a 10% discount before the client signs. The order confirmation shows last month's price. Each of these is a small change with a long tail: one number moves and the line total, the subtotal, the tax and the grand total all have to follow, in the same font, in the same style, right-aligned in the same column. This guide shows two ways to do it in blupdf, by hand and by asking, and where each one shines. It applies to documents you issued or are authorised to change; blupdf's terms do not allow altering records to mislead.
Why invoices are the hardest PDFs to edit
An invoice is a table, and a table is unforgiving. Every amount sits in a column with a shared right edge; every row is a set of cells that belong together; the numbers at the bottom depend on the numbers above them. Most PDF editors treat each piece of text as a loose box: change "2" to "12" and the box grows to the right off the column, the subtotal still says the old figure, and the recipient can see at a glance that something was patched.
blupdf reads the page as rows and columns. A right-aligned amount that gets longer grows to the left and keeps its right edge; the cells on the same row slide to stay aligned; and when blupdf AI makes the change, every number that depends on it is recomputed.
Method 1: retype it yourself
Open the invoice in Studio
Drop the PDF. If it is a scan, the page is recognised and rebuilt as real text when you reach it.
Click the number
The block outlines, the text toolbar appears with the invoice's font and size, and you can type in place. Replace the quantity or the price.
Update the dependents
Click the line total, the subtotal, the tax and the total in turn and retype each one. Keep the printed style: the same currency sign on the same side, the same thousands separator and decimals.
Check the column
Longer amounts grow to the left, so the right edge of the column stays straight. Zoom in with ⌘ and plus to confirm.
Download
Choose Download and keep PDF. The new numbers are real text in the original font.
This is the right method for a single number with no dependents, such as an invoice date, a PO number or an address line.
Method 2: tell blupdf AI
For anything with arithmetic behind it, let the assistant do the bookkeeping:
Open the panel
Click Ask AI in the top bar.
Describe the change
"Change the quantity on the third line to 2." "Set the unit price of the consulting line to $150." "Add a 10% discount before tax." "Change the total to $1,250.00 and adjust the tax to match."
Watch it land
blupdf AI names the cells it changes and writes every dependent number as a formula over the cells it depends on. blupdf computes each formula exactly and prints the result in the style the cell already uses: the same currency sign, separators and decimals, a trailing period if the form prints one. The line total, subtotal, tax and total update together, and a "you saved" line follows the discount.
Review and adjust
The panel lists the changes. Click any block to fine-tune by hand, press ⌘Z to step back, or Undo all to reverse the whole request.
What the assistant will not do is guess. Ask it to "change the price" without a price and it asks which price and to what, instead of inventing a figure. It also reads a row across, so "the Netflix charge" on a statement means the amount on that row, not the first amount on the page.
Running balances and statements
The same mechanism handles a running balance: change the opening balance on a statement and the balance rolls through every row, each one a formula over the previous balance and that row's amount. Change one transaction in the middle and every balance below it follows. Doing that by hand on a 40-row statement is where mistakes creep in; as a set of formulas it is exact.
Keeping the look
Numbers on invoices carry style: "$1,250.00", "1.250,00 €", "(200.00)" for a credit, "-$50.00" for a discount. blupdf reads the style of the number it replaces and reprints the new value the same way. Fonts are kept too: the amount column stays in the invoice's font, or in the closest of blupdf's 35 library families when the font is not embedded, and bold totals stay bold.
Scanned invoices and orders
A scanned or photographed invoice works the same way once it is recognised: the page is rebuilt as real text with its rules redrawn, the amounts sit in real columns, and both methods apply. Check the recognised digits against the scan first with Show original scan; a 6 read as an 8 on a faint print is the kind of thing worth catching before it propagates through a total.
Cost
Opening a digital invoice costs 50 credits per page, once; a scanned page 80. Retyping costs 1 credit per character. A blupdf AI request costs 100 credits plus 1 per character it writes, whether it changes one line or twelve. A one-page invoice with a quantity change and four recomputed totals costs roughly 50 + 100 + 30 = 180 credits by AI, or about 80 by hand. Downloads are free.
FAQ
Will the changed numbers look different from the rest?
No. They are rendered in the invoice's own font and style, in place, and right-aligned amounts keep their right edge.
Can it change the tax rate?
Yes. "Set VAT to 20%" changes the rate line and recomputes the tax and the total; a rate stays a rate and an amount stays an amount.
Is it allowed to edit an invoice?
Correcting a document you issued, updating a quote before it is accepted, or fixing an order confirmation you sent is ordinary business. Altering someone else's records to mislead is not, and blupdf's terms prohibit it.
The reference pages are Editing with blupdf AI and Editing text in a PDF.