How to Join PDF Files into a New One Using pdftk Command on Ubuntu

Installing pdftk on Ubuntu

Install pdftk on Ubuntu.

sudo apt update

sudo apt install pdftk-java

Joining .PDF files

Join .PDF files into a new .PDF file using the following command.

pdftk input1.pdf input2.pdf input3.pdf cat output outfile.pdf

Using a wildcard

You can use a wildcard (*) for input files.

pdftk *.pdf cat output outfile.pdf


How to Change Welcome Screen Display Language in Windows 11

Open Region dialog box

Go to Settings.

Select “Time & language”.

Select “Language & region”.

Select “Administrative language settings”.

Copy settings

In the Region dialog box, select “Administrative” tab.

Click “Copy settings” button.

Mark the check box next to “Welcome screen and system accounts”.

Click “OK” button.

When prompted, click “Restart” button to restart the system.


How to Reload Modules in SageMath

reload() Method

reload() method reloads a previously imported module. It enables you to test a updated version of the module without leaving the sage command line.

sage: reload(module)

Reloading modules for Python 3.4 and above

Use importlib package.

sage: import importlib

sage: importlib.reload(module)


How to Specify the Font of a Text with CSS font-family Property

Serif fonts

Serif fonts have a small stroke at the end of their longer strokes.

Serif fonts examples:

  • Times New Roman
  • Times

How to specify Serif fonts

.serif-class {
  font-family: "Times New Roman", Times, serif;

Sans serif fonts

Sans serif fonts have clean lines without small strokes attached.

Sans serif fonts examples:

  • Arial
  • Helvetica

How to specify Sans serif fonts

.sans-serif-class {
  font-family: Arial, Helvetica, sans-serif;

Monospace fonts

A monospace font is a font in which all the letters have the same fixed width.

Monospace fonts examples:

  • Courier New
  • Courier

How to specify Monospace fonts

.monospace-class {
  font-family: 'Courier New', Courier, monospace;