how install downloaded applications without entering the PC user password

You cannot safely bypass the administrator-password prompt; because this is a secondhand PC and you do not control an administrator account, reset Windows and create your own account before installing applications.

Reset the PC

Warning: This can remove all files, applications, settings, and any remaining data from the previous owner. Back up files that belong to you first. If Windows requests a BitLocker recovery key, obtain it from the seller; without an administrator account, Microsoft recommends resetting the device rather than circumventing the password.^1^

1. At the Windows sign-in screen, select Power.
2. Hold Shift and select Restart.
3. When Windows Recovery Environment appears, select: Troubleshoot → Reset this PC.
4. Select Remove everything. This is preferable for a secondhand computer because it removes existing accounts, applications, files, and settings.
5. Choose:
   • Cloud download for a fresh Windows copy, or
   • Local reinstall to use files already on the PC.
6. Follow the prompts and allow the process to finish. Do not manually power off the computer while it is resetting.
7. During initial setup, create your own Microsoft or local account. For a personally owned computer, select For personal use, not an organization’s work-or-school setup.

Microsoft documents that Remove everything reinstalls Windows and removes personal files, applications, and settings.^2^

After setup, download Adobe Reader directly from Adobe and run its installer. Your new account should be the device’s administrator, although Windows may still display a normal User Account Control confirmation.

If Reset fails or the PC remains organization-managed

Perform a clean installation from Windows installation media. Create the bootable USB on another working computer, start the secondhand PC from that USB, and choose a new installation. A clean installation removes personal files, applications, manufacturer customizations, and existing settings, so back up anything needed first.^3^

If the computer returns to a company sign-in or management screen even after a clean installation, contact the seller. The device may still be registered to the previous organization, which must release it.

Do not enable hidden administrator accounts, disable User Account Control, or use password-bypass utilities. The credential window is a Windows security boundary: installations requiring elevation must receive credentials for an account that already has administrator privileges.

Also note that Windows 10 support ended on October 14, 2025. If the hardware supports Windows 11, upgrade after regaining control of the PC.^2^

References

1. Change or reset your local account password in Windows | Microsoft Support
2. Reset your PC
3. Reinstall Windows with the installation media | Microsoft Support