Can a PDF form calculate totals for you?

Yes, a PDF form can add up its own totals, and PDF by Zaweba sets this up without any scripting. In a field's properties you choose a calculation and a format, such as number, currency, percentage or date, and the app works the result out as the form is filled in. It's free and works offline on Windows.

That makes order forms, expense claims, timesheets and invoices far less error prone, because nobody has to do the sums by hand.

How calculations work in a PDF form

A PDF form can hold instructions that say a field's value comes from other fields. A total box might be the sum of five line amounts, or a VAT box a percentage of a subtotal. When someone types into one of the source fields, the total follows.

Many PDF programs carry these sums out by running scripts inside the file. PDF by Zaweba takes a different route. It carries out the number, currency, percentage, date and time formats, the ranges and the calculations itself, without a script engine, in the order the form specifies. Other scripts don't run. That's a safer way to open forms from strangers, and it still gives you working totals.

Fields you make in the app carry the standard calls that other readers run too, so a form you build with totals in it should add up in the reader the other person uses as well.

Setting up a total

Open the PDF and choose Form, then Prepare form. Add the fields that hold the amounts, giving each a clear name such as Item1, Item2 and so on. Then add the field where the total goes.

Open the total field's properties and go to its calculations. Choose the fields it should add up. Then set the format, picking currency if it's money, so the result shows consistently. Give the source fields the same format, so that what people type looks the same as the total.

Ranges are worth setting too. A quantity field that only accepts sensible values stops a slip of the finger turning into a huge total.

Testing the sums

Think about the order of calculations if one total feeds another. A subtotal, then VAT on the subtotal, then a grand total is a chain, and the app follows the order the form specifies. If a figure looks out of step, check that order.

Make total fields read-only so nobody types over the sum. The Form fields panel lists every field with its page, kind, value and Required or Read-only flags, which is a quick way to confirm you've set things up as intended.

Test with awkward numbers. Type amounts with pennies, leave a line blank and try a zero, and check the total still makes sense. Then clear the form before sending it out.

When the answers come back

Filled forms can have their values exported as XFDF, FDF, XML, CSV or tab-separated text. If you're collecting many orders or claims, the app can merge several data files into one CSV with a row per file, ready for a spreadsheet, so the totals you designed end up in one place.

If you need to send a final copy where nothing can be changed, flatten the form. That draws the fields and their totals into the page and removes them as live objects.

PDF by Zaweba gives you working sums without asking you to learn a scripting language, which is all most forms need.