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Install on Windows

1. Download Kertas-Office-Setup.exe from the download page. One installer works on Intel, AMD and ARM computers.
2. Open the file and follow the steps. Kertas installs for your user only, so no administrator password is needed.

If Windows says it protected your PC: code signing for Kertas is still being set up, so Windows SmartScreen does not recognise the installer yet. Click More info, then Run anyway. Every installer is built by GitHub from the public source, and you can check its checksum first.

Windows shows the publisher as SignPath Foundation, which signs open-source releases after checking they were built from the public code.

To make Kertas open your Word, Excel and PDF files when you double-click them, click Set as default on the Home screen.

Install on macOS

1. Download the version for your Mac from the download page: Kertas-Office-mac-arm64.dmg for Apple silicon (M1 and later), or Kertas-Office-mac-x64.dmg for Intel. Not sure? Apple menu › About This Mac shows Chip (Apple) or Processor (Intel).
2. Open the .dmg and drag Kertas Office into Applications.
3. Open it from Applications. macOS asks once whether to open an app downloaded from the internet; click Open. Kertas is signed and notarized by Apple, so no other warning appears.

To make Kertas open your Word, Excel and PDF files, select a file in Finder, choose File › Get Info, pick Kertas Office under Open with, then click Change All.

Install on Linux

AppImage works on most distributions without installing anything:

1. Download Kertas-Office-linux-x86_64.AppImage.
2. Make it executable: right-click it, open Properties, then Permissions, or run chmod +x Kertas-Office-linux-x86_64.AppImage.
3. Double-click it to start Kertas.

Ubuntu, Debian and derivatives: download kertas-office-amd64.deb and open it with your software centre, or run sudo apt install ./kertas-office-amd64.deb. Kertas then appears under Office in your applications menu.

Open, save and convert files

Drag files onto the window, use Open on the Home screen, or press Ctrl + O. Each file opens in its own tab.

• Writer saves .docx, and opens .doc, .rtf and .odt (saved as .docx).
• Sheets saves .xlsx and .csv, and opens .xls, .xlsm, .xlsb and .ods (saved as .xlsx).
• PDF saves .pdf and can convert a PDF to Word or Excel from the Convert tab.

Opening older .doc and .xls files with full formatting works best when LibreOffice is installed too. If Kertas closes unexpectedly, your unsaved work is offered back under Recovered documents on the Home screen.

How updates work

Kertas checks GitHub for a new version shortly after it starts and every few hours, downloads it in the background and installs it the next time you close the app. You can also click Restart when it says an update is ready.

To check by hand, or to turn automatic updates off, open Help › About Kertas Office. The update check is the only connection Kertas makes; it never sends your files or how you use the app.

Track changes and comments

1. Open the Review tab and click Track changes. Your edits are now recorded as suggestions.
2. To comment, select some text and click New comment. Comments can be replied to and resolved.
3. Accept or reject each change from the Review tab or the side panel.

Changes and comments are saved in the .docx, so colleagues using Word see them too.

Write equations in LaTeX

Click Insert › Equation, or type / and choose Equation. Type LaTeX such as \frac{a}{b} + \sqrt{x} and watch the live preview. Equations are saved as native Word equations, so they stay editable in Word.

Add citations and a bibliography

1. On the References tab, pick a citation style: APA, MLA, Chicago, Harvard or IEEE.
2. Click where the citation goes and add a source, or reuse one you added before.
3. Insert a bibliography where you want the list. It updates as you add citations, and changing the style restyles them all.

Run a mail merge

1. Write your letter, then open the Mailings tab and choose an Excel or CSV list.
2. Insert fields, such as a name or address, from the list's column headings.
3. Preview a few records, then merge to one document or one file per row.

Formulas and functions

Type = in a cell to start a formula, for example =SUM(B2:B10). Hundreds of Excel functions are supported. Use AutoSum on the Home tab for quick totals, or the Formulas tab to browse functions by category. Formulas keep calculating in the background, so large workbooks stay responsive.

Create and refresh a PivotTable

1. Select your data, including the header row.
2. Click Insert › PivotTable, then choose the fields to group by and the values to sum, count or average.
3. When the data changes, click Data › Refresh.

PivotTables are saved as real Excel PivotTables, so they keep working in Excel.

Conditional formatting

Select cells, then open Conditional on the Home tab. Choose highlight rules, top and bottom values, data bars, colour scales or icon sets. Rules update as the numbers change and are kept when you export to PDF.

Export to PDF

Choose File › Export as PDF, or press Ctrl + Shift + E. For a spreadsheet, page setup on the Page Layout tab controls orientation, margins and what fits on a page.

Edit text in a PDF

1. Open the Edit tab and click Edit text.
2. Click a line of the PDF's own text and type over it.
3. Save. Kertas redraws the line in the original font where it is available, otherwise in a close match.

Scanned pages are pictures, so run text recognition first.

Sign a PDF

With a drawn signature: on the Fill & Sign tab, click New signature to draw or type one, then Sign and click where it goes.

With a digital certificate: on the Protect tab, click Digitally sign, choose your .p12 or .pfx file and enter its password. Kertas saves a signed copy. Any later change to the file shows the signature as broken, which is how readers know it was not altered.

Make a scanned PDF searchable

1. Open the Convert tab and click Recognise text.
2. Kertas reads the text on your own computer. Afterwards you can search, select and copy it.
3. Save to keep the recognised text, hidden under the page image, or convert the result to Word or Excel.

Merge, reorder and rotate pages

Click Merge on the Home tab to add pages from other PDFs. On the Organize tab you can rotate, delete, extract and split pages, and you can drag the page thumbnails on the left to reorder them. Bookmarks are kept.